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A revision of the chilodontidae (Gastropoda: Vetigastropoda: Seguenzioidea) of Southern Africa and the south-western Indian ocean.

Ascetostoma providentiae (Melvill, 1909) comb. n. Figs 4F, 5A, 6A, 18-20

Euchelus providentiae: Melvill 1909: 78, pl. 5, fig. 1; Viader 1937: 56; Kaicher 1990: No 5709. Type loc.: Providence Is. (Seychelles group), north east of Madagascar.

not Clanculusprovidentiae: Kosuge & Chino 1998: 79, pl. 26, fig. 1.

Description:

Shell: Trochoid-turbiniform, moderately elevated (L/D=1.04-1.26); teleoconch of 5.0-5.5 rounded whorls; suture indented and somewhat channelled, that between last adult whorl and penultimate whorl inserted at level of second subperipheral cord, but descending below this just prior to aperture; exterior of outer lip with a broad low subterminal thickening. First teleoconch whorl with approx. 20 axial pliculae; 3 spiral cords develop during second whorl (lowest level with abapical suture), and a fourth arising beneath adapical suture near end of whorl; subsequent whorls with further cords arising through intercalation; penultimate whorl with 7-9 cords, sometimes alternating a little in strength, sometimes not; seventh cord usually peripheral; cords well defined, equal to or wider than their intervals. Axial pliculae of first whorl persist on later whorls rendering spiral cords beaded where they cross them; beads of early whorls more or less rounded, but later becoming somewhat axially elongate, those on subsutural cord usually largest; axial pliculae well developed on spire whorls rendering sculpture cancellate, usually less prominent on last adult whorl. Base with 6-7 primary spiral cords and occasional intermediaries, sculptured as above. Peristome markedly oblique, more or less in one tangential plane; aperture subcircular to D-shaped, flattened parietally; columella lip protrudes into aperture as a thickened pillar which bears 2 well-developed teeth separated by a concavity; basal tooth often squarish, upper one somewhat smaller and more rounded; a deep U-shaped notch separates basal tooth from first denticle of basal lip; parietal region with glossy, translucent inductural callus, sculptured with a variable number of ridges extending into aperture; ridges sometimes bifid terminally; a well-developed parietal tooth projects from paries over umbilical depression; umbilicus present, lined and apically plugged with smooth, white callus when mature, conventionally patent in juveniles; umbilical margin thickened, also covered with callus and bearing ridge-like denticles (only in fully mature of specimens); callus slightly raised basally and confluent with flaring margin of outer lip; interior of outer lip with 2 rows of ridge-like denticles (at maximal maturity), the inner row stronger and lying on subterminal thickening of lip interior, the outer row (on non-nacreous flaring lip margin) weaker and less distinct; 2 denticles of inner row, nearest basal columella notch, usually larger; a small rounded or elongate granule may be present on columella near bottom of basal columella notch; interior of aperture nacreous, somewhat angled beneath spiral cords of shell exterior, but not spirally lirate.

Microsculpture (Fig. 19B, C): Early teleoconch whorls with fine vermiform spiral threads; microsculpture of subsequent whorls often completely obscured by encrusting organisms; little evidence of any superficial intritacalx deposit and scratch-like sculpture scarcely evident; microsculpture instead comprising irregular, somewhat oblique, vermiform threads, most noticeable on the spiral cords (Fig. 19B).

Protoconch (Fig. 19C): Translucent white, peripherally tinged with orange; diameter ca 240 [micro]m; somewhat globose and protruding slightly above first teleoconch whorl; sculptured with 3 fine, widely spaced, spiral threads, between which lie numerous, fine, close-set, oblique, axial threads; terminal lip with a well-developed angular projection just above mid-whorl.

Colour: Most specimens uniformly rich orange-brown with darker spots on spiral cords of second and third whorls; occasional specimens with alternating darker and lighter blotches below suture; cord intervals faintly iridescent; umbilical region white; pigmentation of old, dead shells frequently rather more pinkish/purplish brown. Shell exterior of live-taken specimens usually more or less entirely covered with a thin, brownish or blackish, spiculiferous, encrusting sponge (Fig. 18E).

Dimensions: Greatest length 9.0 mm, greatest diameter 8.0 mm, but size at maturity evidently variable; some specimens of length ca 7.0 mm possess mature apertural dentition.

Operculum (Fig. 4F): Initially tightly multispiral, but whorls broadening with growth and becoming more openly multispiral.

Radula (Fig. 19D, E): Formula [infinity]+4+1+4+[infinity]; ca 75 transverse rows of teeth. Rachidian with trigonal cusp and well-developed hood; base of cusp with weak transverse ridge; cutting edge coarsely dentate, central denticle largest, lanceolate and with 3 or 4 smaller denticles on each side. Lateral tooth cusps with an elongate, rather spathulate central denticle and relatively coarse secondary denticles on outer margin, inner margin with few if any denticles. Inner marginals more slender with a recurved, dentate cusp, the denticles on outer margin extending some way down shaft; middle marginals very slender, but outermost ones shorter, broader and very delicate.

External anatomy (Figs 5A, 6A): Head-foot with extensive dark brown to black pigmentation in living animal; cephalic tentacles more or less uniformly dark; blackish colour of neck lobes and epipodial tentacles contrasting with whitish upper parts of foot. Cephalic lappets finely digitate, not meeting in mid-line; snout laterally expanded, transversely striped with black, lips split mid-ventrally; right post-ocular peduncle relatively small, arising from base of eyestalk; subocular tentacle not evident; right neck lobe with approx. 5 closely spaced tentacles anteriorly (increasing in size from first to last) followed by 2 or 3 more widely spaced ones; left neck lobe with numerous, closeset tentacles along most of its length, more or less similar in size; epipodial fold with approx. 10 tentacles of various sizes, the larger ones each with a basal epipodial sense organ; epipodial sense organs not evident beneath neck lobes, but some larger neck lobe tentacles with a pale basal spot that may represent such a structure.

Type material: Melvill (1909) stated that he had examined two specimens and selected the larger as the 'type' [holotype]. The second specimen would therefore be a paratype. Two specimens were originally registered under NHMUK 1910.3.17.2-3, but only one is now present. This is smaller than the dimensions given by Melvill and is presumably the paratype; length 6.6 mm, diameter 5.9 mm. It is a subadult specimen in which the apertural dentition is not fully developed (Fig. 18G, H).

Additional material examined (all NMSA unless indicated otherwise): MADAGASCAR: W Banc du Leven (12.5333[degrees]S 47.6675[degrees]E), -35-150 m, Benthedi Exped'n, st'n 5, dredged (MNHN); west of Nosy Be (13.417[degrees]S 47.950[degrees]E), -71-158 m, Campagne Miriky, st'n DW3230, dredged, 03.vii.2009 (MNHN). REUNION: off Etang-Sale-les-Bains, Marion-Dufresne 32, st'n DC176 (21.3333[degrees]S 55.1833[degrees]E), -165-195 m, dredged, 1982 (MNHN). MOZAMBIQUE: Sofala Bank (approx. 20.123[degrees]S 35.543[degrees]E), -110-145 m, expisce, v.2007 (J. Rosado coll'n); between Beira and Bazaruto (approx. 20.58[degrees]S 35.73[degrees]E), -95-125 m, ex pisce (J. Rosado coll'n); off Lacerda Lighthouse (25.56167[degrees]S 32.84472[degrees]E), -72-75 m, dredged, vii.2008 (J. Rosado coll'n); off Ponta Techobanine (26.68132[degrees]S 32.95093[degrees]E), -60-100 m, dredged J. Rosado, xii.2005 (D. Slater coll'n). SOUTH AFRICA: KwaZulu-Natal: off Kosi River mouth (26.9100[degrees]S 32.9433[degrees]E), living, -75 m, sandstone, marine growths, dredged NMDP, RV Meiring Naude, st'n ZA13, 7.vi.1987 (D9009, E1413); SE of Kosi estuary mouth (26.9167[degrees]S 32.9300[degrees]E), -65 m, sponge, gorgonians, medium sand, dredged NMDP, RV Meiring Naude, st'n ZA12, 7.vi.1987 (D8018); off Boteler Point (27.0083[degrees]S 32.9117[degrees]E), living, -50 m, coral rubble, lithothamnion, dredged NMDP, RV Meiring Naude, st'n ZB7, 6.vi.1987 (E2943); ditto (27.013[degrees]S 32.905[degrees]E), -50 m, dead coral rubble, lithothamnion, dredged NMDP, RV Meiring Naude, st'n ZB2, 6.vi.1987 (D9199) ditto (27.0117[degrees]S 32.9200[degrees]E), living, -70 m, rocks and sand, dredged NMDP, RV Sardinops, st'n ZB19, 6.vi.1990 (S4904, S8715, S8961); ditto (27.0133[degrees]S 32.9183[degrees]E), -70 m, some coarse sand, some shell rubble, dredged NMDP, RV Meiring Naude, st'n ZB4, 6.vi.1987 (D7415); ditto (27.0183[degrees]S 32.9200[degrees]E), -78 m, coarse sand, dredged NMDP, RV Meiring Naude, st'n ZB6, 6.vi.1987 (D7475); ditto (27.0183[degrees]S 32.9183[degrees]E), living, -69-73 m, sponges, rocks and sand, dredged NMDP, RV Sardinops, st'n ZB20, 6.vi.1990 (S5026); ditto (27.0400[degrees]S 32.9150[degrees]E), living, -75 m, rocks, sand, gorgonians, dredged NMDP, RV Sardinops, st'n ZB22, 6.vi.1990 (S5381); ditto (27.0500[degrees]S 32.9117[degrees]E), -78 m, marine growths, dredged NMDP, RV Sardinops, st'n ZB23, 6.vi.1990 (S6651); off Dog Point (27.1000[degrees]S 32.8883[degrees]E), living, -74 m, sandstone rubble and gorgonians, dredged NMDP, RV Sardinops, st'n ZC10, 7.vi.1990 (S6485); ditto (27.1083[degrees]S 32.8817[degrees]E), living, -70 m, sandstone conglomerate, dredged NMDP, RV Meiring Naude, st'n ZC3, 4.vi.1987 (D6477, E1743); ditto (27.1267[degrees]S 32.8733[degrees]E), living, -76 m, sandstone rubble and gorgonians, dredged NMDP, RV Sardinops, st'n ZC12, 7.vi.1990 (S8968); off Rocktail Bay (27.1850[degrees]S 32.8483[degrees]E), -100 m, sand, dredged NMDP, RV Sardinops, st'n ZD4, 7.vi.1990 (S5182); ditto (27.1900[degrees]S 32.8500[degrees]E), -100 m, sandstone rubble, dredged NMDP, RV Meiring Naude, st'n ZD1, 4.vi.1987 (D7597); ditto (27.1900[degrees]S 32.8433[degrees]E), living, -75 m, sandstone rubble, dredged NMDP, RV Meiring Naude, st'n ZD2, 4.vi.1987 (D6361, D9154); SE of Rocktail Bay (27.1917[degrees]S 32.8400[degrees]E), living, -78 m, sandstone rocks, dredged NMDP, RV Sardinops, st'n ZD10, 8.vi.1990 (S4639); ditto (27.2017[degrees]S 32.8300[degrees]E), living, -60 m, coarse sand, dredged NMDP, RV Sardinops, st'n ZD9, 8.vi.1990 (V894); NE of Lala Neck (27.2150[degrees]S 32.8283[degrees]E), living, -66-71 m, coarse sand, sandstone rocks, dredged NMDP, RV Sardinops, st'n ZD7, 8.vi.1990 (S6137); off Lala Neck (27.2292[degrees]S 32.8217[degrees]E), living, -72 m, slightly muddy sand with pennatulids, dredged NMDP, RV Sardinops, st'n ZDD1, 7.vi.1990 (S7335); SE of Lala Neck (27.2433[degrees]S 32.8133[degrees]E), living, -74 m, sandstone rocks, dredged NMDP, RV Sardinops, st'n ZDD2, 7.vi.1990 (S7232); off Hully Point (27.343[degrees]S 32.778[degrees]E), living, -60 m, shell rubble, dredged NMDP, RV Meiring Naude, st'n ZF4, 5.vi.1987 (D7332); off Sodwana Bay (27.530[degrees]S 32.717[degrees]E), living, -70 m, coral rubble, dredged NMDP, RV Sardinops, st'n ZH22, 2.vi.1990 (W7477); off Jesser Point (27.5467[degrees]S 32.7100[degrees]E), living, -68 m, sponge, coral rubble, dredged NMDP, RV Meiring Naude, st'n ZH3, 3.vi.1987 (D6512); ditto (27.5533[degrees]S 32.7133[degrees]E), living, -85 m, sponge, coral rubble, dredged NMDP, RV Meiring Naude, st'n ZH4, 3.vi.1987 (D6789); off Sodwana Bay (27.5567[degrees]S 32.7133[degrees]E), -77 m, dead coral rubble, dredged NMDP, RV Sardinops, st'n ZH19, 2.vi.1990 (S4781); ditto (27.5833[degrees]S 32.6967[degrees]E), -70 m, medium sand, dredged NMDP, RV Meiring Naude, st'n ZH16, 9.vi.1987 (D8441); Leadsman Shoal (27.8000[degrees]S 32.6167[degrees]E), -100 m, dredged A.D. Connell, iv.1980 (B4054); off Gipsy Hill (27.8117[degrees]S 32.6567[degrees]E), -100-125 m, broken shell, dredged NMDP, RV Meiring Naude, st'n ZK9, 11.vi.1988 (E3248); SE of Mission Rocks (28.2917[degrees]S 32.5433[degrees]E), -50 m, old coral rubble, lithothamnion, dredged NMDP, RV Meiring Naude, st'n ZN1, 10.vi.1988 (E4640).

Distribution and habitat (Fig. 20): Islands of the western Indian Ocean (southern Seychelles group and Mascarenes) and the Mozambique Channel south to north-eastern South Africa (28.3[degrees]S, off Mission Rocks); -35-195 m (living specimens -50-85 m). In Zululand this species appears to inhabit hard substrata beyond the line of the near-shore reef system, where the sea floor is composed of fragmented sandstone or coral rubble, and is generally rich in marine life. Evidently a mid to outer continental shelf species throughout its range and not part of the shallow-water coral reef biota.

Remarks: This species is very similar to Euchelus ringens Schepman, 1908 from the Sulu Archipelago, Indonesia, and the two may eventually prove to be synonyms. The columella lip of the holotype of E. ringens (Fig. 68A, B) is somewhat damaged (perhaps due to occupation by a hermit crab) and looks rather deformed. Compared with southwestern Indian Ocean material it differs in being slightly less elevated and in having a narrower umbilicus; there are also minor differences in terms of coloration and aperture characters. In the absence of data on variation in Indonesian material, I have chosen, to err on the side of caution and maintain Ascetostoma providentiae as a distinct species. There can be no doubt, however, that E. ringens is also a species of Ascetostoma.

A. providentiae is easily distinguished from the other southern African chilodontid taxa by its rounded whorl profile, very strong, complex apertural dentition and patent, callus lined umbilicus. 'Clanculus' crassilabrum Sowerby, 1905 (Fig. 68C, D) from Sri Lanka has a similar overall facies, but lacks the unusual umbilical features of Ascetostoma and is probably closer to Herpetopoma. Also similar is Herpetopoma rubrum (A. Adams, 1853), from Japan to SE Asia, which is likewise often vividly coloured, but in that species the inductural callus does not extend over the umbilical region and the umbilicus remains conventionally patent even at full apertural maturity. The Japanese Euchelus lischkei Pilsbry, 1904 also resembles A. providentiae in size, shape and sculpture, but has a much weaker basal columella tooth and has a simple, patent umbilicus. The Philippine material identified under this name (as Clanculus) by Kosuge and Chino (1998) is not in fact referable to this species.

The Cretaceous Chilodonta (Agathodonta) africana Rennie, 1930 from the Pondoland coast, Eastern Cape (holotype, SAMC 8630) is superficially similar to A. providentiae, but it has finer granules above the periphery, distinct prosocline pliculae below the suture and a smoother base. It has a well-developed tubercle on the basal lip separated from the columella by a U-shaped notch, but no details of its umbilicus are apparent.

Genus Euchelus Philippi, 1847

Euchelus: Philippi 1847: 20. Type species: Trochus quadricarinatus [Chem.] Holten, 1802 [=Trochus asper Gmelin, 1791], by subsequent designation (Herrmannsen 1847: 430).

Species of Euchelus s.s. are generally larger shelled than those of Herpetopoma, have a single weak columella tooth and lack a deep U-shaped notch at the base of the columella. Evidently Euchelus s.s. is scarce in the south-western Indian Ocean. Only two species have been recorded from the region and I have seen no further material referable to this genus.

Euchelus alabastrum (Reeve, 1858) Fig. 21

Trochus (Euchele) alabastrum: Reeve 1858 in 1857-58: 209, pl. 38, figs 1a, b; Pilsbry 1890 in 1889-90: 448. Type loc.: Island of Diego Garcia.

Euchelus alabastrum: Pilsbry 1890: 344. not Trochus alabastrum: Beck ms Philippi 1847 in 1846-55: pl. 15, fig. 14; idem 1849 in 1846-55: 9 [= Margarita alabastrum: Beck ms Loven, 1846 = Calliostoma occidentale (Mighels & C.B. Adams, 1842)].

There is no type material for this species in the NHMUK and although Reeve mentioned additional material in the Cuming collection, no specimens identified under this name could be found in the NHMUK general collection. Nonetheless, two specimens labelled 'triangulata var.' (without locality), from the Cuming collection, bear considerable resemblance to Reeve's original figure of Trochus alabastrum (Fig. 21A). The larger of the two is here figured for comparison (Fig. 21B). Like alabastrum it is chalky-white with small spots (now much faded and pale purple-brown rather than black) on the spiral keels.

This material represents pale, particularly strongly keeled individuals of the quadricarinatus form of the highly variable Euchelus asper (Gmelin, 1791). Although it can not be considered type material for T. alabastrum, its resemblance to the description and original figure of the latter strongly suggests that it may have been the Cumingian material referred to by Reeve. There can be little doubt that it is conspecific therewith. I therefore propose that Trochus alabastrum Reeve, 1958 be considered a synonym of Euchelus asper (Gmelin, 1791) and that it represents the form quadricarinatus (Holten, 1802) (cited figure reproduced in Fig. 21C) of that species. Monodonta tricarinata Lamarck, 1822 is already established as another synonym (Fischer 1878 in 1875-80). This form of the species is evidently widespread in the Indo-West Pacific, occurring as far east as Japan (Sasaki 2000). It was also recorded from Durban by Sowerby (1897), but it seems more probable that this was a misidentified or mislocalised specimen. Fresher material from Thailand is illustrated for comparison (Fig. 21D) and an additional figure was provided by Poppe and Tagaro (2008: pl. 43:8). The extent of variation within E. asper is considerable and requires further study in order to evaluate its significance and to determine if it is genetically, environmentally or sexually determined.

The original Trochus alabastrum material described by Reeve (1858) came from the collection of Sir David Barclay, which was sold at auction in 1891 (Dance 1986). Some types from this collection were subsequently purchased by the NHMUK from G.B. Sowerby (3rd), but the whereabouts of others is not known (J. Pickering pers. comm., Feb. 2011).

Euchelus atratus (Gmelin, 1791)

Turbo atratus: Gmelin 1791: 3601, No 53. Type loc.: Nicobar Islands.

Euchelus atratus: Pilsbry 1890 in 1889-90: 439 (further references and synonymy), pl. 38, fig. 22; Thiele 1917: 563; Drivas & Jay 1988: 36, pl. 3, fig. 6.

Thiele (1917) and Drivas & Jay (1988) recorded this species from the Comoros and Reunion respectively. A single specimen is present in the Jay coll'n (MNHN), but it is in very poor condition, most of the surface sculpture having flaked off. However, what remains is of a pale colour, which combined with the fact that the specimen has a closed umbilicus, suggests that it may not in fact be referable to E. atratus. In the absence of additional material in better condition I cannot confirm the occurrence of this species in the south-western Indian Ocean.

Genus Herpetopoma Pilsbry, 1890

Huttonia: Kirk 1882: 282 [non Pickard-Cambridge, 1880 (Araneae) nec Marshall, 1896 (Diptera)]. Type species: Euchelus bellus Hutton, 1873, by subsequent designation (Pilsbry 1890 in 1889-90: 429).

Herpetopoma: Pilsbry 1890 in 1889-90: 430, 445. Type species: Euchelus scabriusculus Adams & Angas in Angas, 1867, by original designation.

The type species of Herpetopoma, Euchelus scabriusculus Adams & Angas in Angas, 1867, from southern and south-eastern Australia, is a small gemmate species with a simple, open umbilicus bordered by a strongly beaded spiral cord. The columella is likewise relatively simple with a single well-developed tooth at its base. Another welldeveloped tooth is situated on the basal lip, close to its junction with the columella, the space between these teeth forming a deep U-shaped notch. The inner margin of the outer lip is set with numerous small, ridge-like denticles and the operculum is openly multispiral, with a broad growing margin (Fig. 4H).

Herpetopoma has frequently been treated as a subgenus of Euchelus, but like most more recent authors, I consider it to represent a distinct radiation and to be worthy of recognition at generic level. Species of Euchelus s.s. are generally larger and have an operculum with fewer, more rapidly expanding whorls (see above). Although they may have a single simple tooth/denticle at the base of the columella, they mostly lack the characteristic pattern of two teeth at the junction of the columella and basal lips, separated by a U-shaped notch, which is typical of Herpetopoma. Other taxa (e.g. Ascetostoma, Clypeostoma and Danilia) that exhibit this last feature have additional characters, which set them apart from Herpetopoma.

However, even when recognised as a genus itself, Herpetopoma, may prove to be a composite taxon, given the diversity of shell form evident in the species assigned to it. I have reasonable confidence that H. instrictum, H. seychellarum, H. serratocinctum and H. stictum are correctly placed in this genus and refer them to Herpetopoma sensu stricto. However, I am less certain about H. helix, H. ?naokoae and H. xeniolum and thus consider them Herpetopoma sensu lato. The protoconch is more exsert and evidently less strongly sculptured, the juvenile microsculpture sometimes granular rather than vermiform and, at least in H. helix, the operculum is tightly multispiral throughout.

No well preserved alcohol material is available for any of the local species of Herpetopoma and thus details of the external anatomy are not available. However, I have been able to extract a radula from H. helix as well as from dried specimens of the type species loaned from the Australian Museum, Sydney. Details of the latter are given below.

Radula (Fig. 22): Formula [infinity]+(3-4)+1+(3-4)+[infinity]; ca 55 transverse rows of teeth; transition from lateral to marginal series relatively clear. Rachidian with broad, trigonal cusp and well-developed hood; cusp with strong transverse ridge at its base, this generally concave due to medial indentation near cusp base; cutting edge coarsely dentate, central denticle largest, lanceolate, with 2-4 smaller denticles on each side. Lateral teeth progressively decreasing in size from first to last, but not markedly so; one specimen with 3 pairs of laterals per row, another with four; cusp elongate-trigonal to spathulate, bearing coarse lateral denticles on both margins (3-6). Marginals longer and more slender than laterals, but relatively shorter than in other genera; inner marginals distinctive in having a slender, recurved cusp with a few short, barb-like denticles near the tip on inner margin and a series of much longer, close-set, curved denticles on outer margin, the central part of the cusp appearing as a rib-like structure from which the two series of denticles project (Fig. 22C); remaining marginals with smaller, ladle-shaped cusps with a finely pectinate margin, the outermost one with a somewhat enlarged cusp (Fig. 22D).

Key to species of Herpetopoma in the south-western Indian Ocean

1 Basal columella tooth a well-developed peg with a deep U-shaped notch separating it from the first (usually the largest) tooth inside the basal lip (Fig. 23) 2

--Basal columella tooth smaller and roundly trigonal; U-shaped notch at base of columella relatively shallow (Fig. 32) 5

2 Umbilicus remaining patent in adult 3

--Umbilicus closed in adult 4

3 Adult shell length exceeding 5.0 mm; spire trochiform, usually with reddish brown markings instrictum

--Adult shell length less than 4.0 mm; spire low, evidently without colour pattern seychellarum

4 Shell small, adult length rarely >3.0 mm; profile globose with a well-developed serrate spiral cord at periphery; coast of tropical East Africa serratocinctum

--Shell larger, adult length >3.0 mm; spire profile more trochiform; peripheral cord not enlarged or conspicuously serrate; Mascarene Islands stictum

5 Sculpture relatively coarse with 3 strong spiral cords above and including periphery; beads on spiral cords axially elongate helix

--Sculpture fine with 4 or more spiral cords above and including periphery; beads more or less rounded 6

6 Shell relatively low-spired, L/D <1.23; labral denticles largely restricted to thickened inner lip; whorls rounded, sculpture relatively coarse ?naokoae

--Shell higher-spired, L/D>1.23, some labral denticles extending into aperture as in-running ridges; whorls rather flat-sided, sculpture fine xeniolum

Herpetopoma (s.s.) instrictum (Gould, 1849) Figs 4G, 23-25

Trochus (Monodonta) instrictus: Gould 1849 in 1846-50: 107; 1852: 190, pl. 13, fig. 225a-c; 1862: 59; Johnson 1964: 92. Type loc.: Pacific Islands.

Monodonta alveolata: A. Adams 1853: 176. Type loc.: 'Guidulman, island of Bohol, rocky ground, 60 fathoms [-110 m]; Baclayon, island of Bohol, under stones, low water; island of Capul, on the reefs at low water'.

Monodonta bourcierei: Crosse 1863: 178, pl. 4, fig. 6; Pilsbry 1890 in 1889-90 [= Trochus instrictus Gould, 1849]. Type loc.: New Caledonia.

Turcica instricta: A. Adams 1864b: 143.

Trochus (Euchelus) alveolatus: Smith 1876: 559.

Trochus bourcierei: Fischer 1878 in 1875-80: 249, pl. 84, fig. 3.

Euchelus alveolatus: Melvill & Sykes 1897: 172; Kaicher 1990: No 5706, syntype.

Euchelus instrictus: Pilsbry 1890 in 1889-90: 440, pl. 67, figs 62, 63; Hedley 1899: 405; Hidalgo 1904-5: 256; Shirley 1911: 96; Cernohorsky 1978b: 33, pl. 8, fig. 6 [= Monodonta alveolata Adams, 1853]; Kaicher 1990: No 5705, holotype; Wells & Slack-Smith 1986: 44; Jansen 1996: 7, No 21 [doubtful]; Kosuge & Chino 1998: 78, pl. 25, fig. 3 [doubtful]; Chang 2003: 4, figs C-F.

Monodonta bourcieri [sic]: Smith 1897: 232.

Euchelus intricatus [sic]: Schepman 1908: 71.

Euchelus (Euchelus) alveolatus: Solem 1953: 218.

Euchelus (Euchelus) instrictus: Hirase & Taki 1954: pl. 70, fig. 6; Solem 1958: 217.

Euchelus instricta: Habe 1964: 10, pl. 4, fig. 14.

Euchelus (Herpetopoma) instrictus: Ladd 1966: 33, pl. 3. figs 11-13; Springsteen & Leobrera 1986: 36, pl. 5, fig. 10.

Euchelus bourcieri [sic]: Kaicher 1990: No 5707, type.

Euchelus (Vaceuchelus) instrictus: Fukuda 1993: 24, pl. 6, fig. 70.

Herpetopoma instricta: Wilson 1993: 68; Higo et al. 1999: 52, No G280; Sasaki 2000: 57, No 18; Vilvens & Heros 2003: fig. 5; Taylor & Glover 2004: 264; Heros et al. 2007: 209.

Herpetopoma instrictum: Poppe et al. 2006: 37, pl. 10, fig. 4; Poppe & Tagaro 2008: 174, pl. 32, figs 2, 6. not Euchelus cf. instrictus: Orr Maes 1967: 103, pl. 3, fig. E.

Description:

Shell: Trochoid-turbiniform, moderately elevated (L/D=1.10-1.25); teleoconch of up to 6.5 whorls; spire whorls somewhat flat-sided; suture strongly indented, inserted at level of subperipheral cord and thus appearing somewhat channelled, descending slightly just prior to outer lip. First teleoconch whorls sculptured with curved axial pliculae; 2-3 spiral cords arise during second whorl, and additional ones with subsequent growth; penultimate whorl with approx. 5 well developed cords, a sixth level with suture; subsutural cord strongest, but becoming distinctly weaker just behind outer lip; cords equal to or narrower than their intervals. Axial pliculae of first whorl persist on later whorls producing a distinct cancellation and rendering spiral cords granular where they cross them; granules of subsutural cord usually largest, becoming smaller and more numerous toward periphery; interstices more or less square on spire whorls, becoming axially elongate on last adult whorl, particularly so just behind outer lip. Base similarly sculptured with approx. 6 spiral cords, the last of which forms umbilical margin; umbilicus remaining open at maturity (very occasionally almost occluded by reflected columella). Peristome oblique; aperture D-shaped, flattened parietally; columella thickened, bearing a low bulge in the mid region and a well-developed, peg-like tooth basally; a deep U-shaped notch separates basal columella tooth from first denticle of basal lip; parietal callus not extending far beyond aperture, bearing spiral ridges; margin of outer lip somewhat flaring, the edge finely and rather irregularly crenulate; interior of outer lip with a subterminal thickening which is set with relatively strong, in-running, ridge-like denticles, these become weaker toward lip margin and develop finer intermediaries (at maximal maturity); denticles not extending far into aperture, one nearest basal columella notch usually larger; 1 or 2 small rounded granules may be present on columella near bottom of basal columella notch; interior of aperture nacreous; exterior of outer lip sometimes with a broad low subterminal thickening, but lacking a rib-like varix.

Microsculpture (Fig. 24A-C): Juvenile shell with vermiform spiral threads; later whorls with close-set, scratch-like marks beneath intritacalx.

Protoconch (Fig. 24A, C): White, more or less level with first teleoconch whorl or at most weakly exsert, with a weak apical beak; diameter 220-240 [micro]m; terminal lip distinctly convex; superficial sculpture well developed, arranged in irregular axial lines, with a weak spiral element.

Colour: White to yellowish white, later whorls with reddish to brown spots, blotches or axial flames; markings generally browner in fresh specimens; a white to dirty brown intritacalx is present in fresh specimens but this is worn off in most museum material. Shell surface often encrusted by other marine organisms.

Dimensions: Largest specimen seen, length 11.9 mm, diameter 10.0 mm (lectotype of Monodonta alveolata A. Adams, 1853).

Operculum (Fig. 4G): Initially tightly multispiral, but whorls broadening with growth and becoming more openly multispiral.

Radula and external anatomy: Unknown except for some brief comments on the external anatomy made by A. Adams (1864b). A figure of a living specimen was also provided by Sasaki (2000: 56).

Type material: Holotype of Trochus instrictus Gould, 1849, in USNM (5625) (Fig. 23A, B see also Kaicher 1990), length 8.3 mm, diameter 7.5 mm (measured from photograph scale, dimensions given by Gould equate to 9.5 x 7.6 mm); four syntypes of Monodonta alveolata A. Adams, 1853 in NHMUK (196872), the best of which is here figured and designated lectotype, length 11.9 mm, diameter 10.0 mm (Fig. 23E, F); holotype of Monodonta bourcierei Crosse, 1863 in NHMUK (96.12.1.13), length 8.6 mm, diameter 7.0 mm (Fig. 23G, H).

Regional material examined: KENYA: Kilifi (3.60236[degrees]S 39.81190[degrees]E), ca -4 m, lagoon inshore of coral reef, sand from base of coral outcrops, D. Herbert, 20.xii.1991 (K8265); Shimoni, SE of Wasini Is. (4.65[degrees]S 39.39[degrees]E), J.D. Taylor (NHMUK); Shimoni area, Shungalunzi (1.2 km east of Shimoni) (4.67[degrees]S 39.41[degrees]E), J.D. Taylor (NHMUK). COMOROS: Mayotte (12.87[degrees]S 45.09[degrees]E), V.W. MacAndrew coll'n (NHMUK). MADAGASCAR: Ouest Cap Antsirabe (25.04167[degrees]S 46.99500[degrees]E), -4-5 m, fond rocheux en limite de platier, Exped'n Atimo Vatae, st'n TS12, 9.v.2010 (MNHN); Pointe d'Ambero (25.11167[degrees]S 46.83167[degrees]E), intertidal substrat dur, mode battu, Exped'n Atimo Vatae, st'n TM16, 08.v.2010 (MNHN); Baie des Galions (25.1483[degrees]S: 46.7567[degrees]E), intertidal, platier rocheux et sable, Exped'n Atimo Vatae, st'n TM21, 12.v.2010 (MNHN). MOZAMBIQUE: Pemba (12.937[degrees]S 40.521[degrees]E), J. Rosado, x.1993 (NMSA L2055); ditto, living amongst dead coral in shallow subtidal, J. Rosado, xi.2010 (NMSA L8398); ditto, Praia do Uimbe, amongst dead coral in shallow subtidal, J. Rosado, xi.2010 (j. Rosado coll'n); Conducia Bay (14.9128[degrees]S 40.7178[degrees]E), K.J. Grosch, purch. ix.1975 (NMSA J4175).

Other material examined: ANDAMAN ISLANDS: Port Blair area, E.M. Man (NMSA F7170); same, Winckworth coll'n (NHMUK). PHILIPPINES: Matabugkay, 115 km SSW of Manila, short algae on reef flat, W. Ponder (AMS); Punta Engano, Mactan Is., Cebu, deep-water shell grit, F.J. Springsteen (NMSA K2549); Palawan Is., Tadio Is., coral rubble washings, low tide patch-reef, W. Ponder (AMS); beach at Santa Cruz Is., off Zamboanga, Mindanao, A.J. Meagher (AMS C.71800); west of Zac Is., Pearl Bank, Sulu Archipelago, coarse sand (WAM). PAPUA-NEW GUINEA: Bougainville Straits, W. Burrows (AMS); East Cape, Papua, H.T. Williams (AMS); Kuia Is., Lusancay Islands, Trobriand group [Kiriwina], Ponder & Colman (AMS); ditto, near Okaiboloma village, rubble and algae washings, living Ponder & Colman (AMS). AUSTRALIA: Western Australia: Kendrew Is., Dampier Archipelago, -27-28 m (WAM); ditto, in Caulerpa washings from reef flat (WAM); ditto, transect 1, C.o.T. survey, -67-68 m (WAM); ditto, transect 2, C.o.T. survey, -146-147 m (WAM); ditto, under rocks (WAM); Lighthouse Beach, NW Cape, shell sand, L. Figgis (AMS C.304705); north of Tantabiddi, NW Cape, at base of outer reef slope (WAM); Turtle Bay, NW Cape, J. Hewitt (WAM); Quobba, Hewitt, Plant, Buick (WAM). Queensland: Bramble Cay, Torres Strait, C. Hedley (AMS C.051290); Darnley Is., Torres Strait, under stones on shore, Chevert Exped'n (AMS C.061508); Murray Is., Torres Strait, C. Hedley (AMS C.29253); Rocky Isle, off Cape Flattery, C. Hedley (AMS C.041235). Great Barrier Reef: south end of Lizard Is., -15 m, on outer side of reef, W. Ponder (AMS); Three Isles, north of Cooktown, Iredale (AMS); Arlington Reef, intertidal, living, I. Loch (AMS); Low Isles, living, British GBR Exped'n 1928 (AMS C.304699); Low Isles, J. Hewitt (WAM); Michaelmas Cay, GBR Boring Exped'n 1926 (AMS C.304704); North West Is., Capricorn Group, J. Kerslake coll'n (AMS C.304701). CORAL SEA: NE Herald Cays (16.95[degrees]S 149.17[degrees]E), D.F. McMichael & J.C. Yaldwyn, xi.1964 (AMS C.304700). NEW CALEDONIA: Noumea, R.C. Rossiter (AMS C.003734). TUVALU: Funafuti Atoll, R. Soc. Coral Boring Exped'n 1896 (AMS C.005838). FIJI: Nadi Bay, Viti Levu, -9-35 m, J. Laseron (AMS).

Distribution and habitat (Fig. 25): Indo-West Pacific; from southern Japan, SE Asia and the south-western Pacific to western Australia, the Andaman Islands and East Africa; in the western Indian Ocean extending south to southern Madagascar, but not yet recorded from central or southern Mozambique, or South Africa. Recorded from Quaternary deposits in the Marshall Islands (Ladd 1966). Little information regarding the habitat of living animals is available. Adams (1864b) reported a living specimen dredged at 55 fath. [-100 m] off southern Japan, but most of the specimens available (live and dead collected) have come from near-shore reef systems with a coralline facies (AMS and WAM material). Wilson (1993) gave the bathymetric distribution as intertidal to -140 m, but did not specify whether this concerned living or dead material. Sasaki (2000) cited the habitat as intertidal and upper subtidal, on coral rubble, and in northern Mozambique, J. Rosado has collected it alive amongst dead coral in the shallow subtidal.

Remarks: The synonymy of Trochus instrictus Gould, 1849,Monodonta alveolata Adams, 1853 and M. bourcierei Crosse, 1863 has been noted previously on several occasions (e.g. Pilsbry 1890 in 1889-90; Cernohorsky 1978b; Kaicher 1990). Other species with similar apertural dentition and umbilical form include H. crassilabrum (Sowerby, 1905) from Sri Lanka, H. exasperatum (A. Adams, 1853) from the Philippines, H. gemmatum (Gould, 1845) from Hawaii, and H. seychellarum (G. & H. Nevill, 1869). H. exasperatum (Fig. 68E, F) and H. seychellarum (Fig. 29), however, are much less elevated, whilst H. gemmatum and H. crassilabrum (Fig. 68C, D) have more rounded whorls with relatively close-set and more obviously beaded spiral sculpture, the latter also has a more strongly developed upper columella denticle and a partially occluded umbilicus; all are smaller than H. instrictum. Amongst south-western Indian Ocean chilodontid taxa, only H. seychellarum retains a simple and deep umbilicus when mature, but that species is considerably smaller and more depressed.

Herpetopoma (s.s.) serratocinctum sp. n. Figs 26-28

Etymology: From Latin serratus (toothed like a saw) and cinctum (a belt or girdle); in reference to the strong, toothed peripheral cord.

Description:

Shell: Small, turbiniform, relatively solid; length more or less equal to diameter (L/D= 0.97-1.1); teleoconch of approx. 3.5 whorls; whorls rounded at periphery, but with a strong peripheral spiral cord; suture indented, level with subperipheral cord, but descending below this immediately prior to aperture in mature individuals; first teleoconch whorl initially sculptured with strong, widely spaced, curved, axial pliculae; pliculae becoming thinner and more close-set after one quarter whorl; 2 spiral cords arising in latter half of whorl; both axial and spiral sculpture strengthening during second whorl and a third spiral cord arising beneath adapical suture; axial pliculae prosocline, more close-set than spiral cords creating obliquely rectangular interstices; cords with rounded nodules where crossed by axial pliculae; 2 further spiral cords arise by intercalation during third whorl, end of penultimate whorl thus with 5 spiral cords of alternating strength above suture; interstices more nearly square; beads on peripheral cord, well developed, stronger, more angular and fewer in number than on other cords (approx. 25 on last adult whorl), but those in final quarter whorl smaller, less angular and more close-set. Base with 4 primary spiral cords, a weaker fifth beneath peripheral cord and a sixth mostly hidden by reflected columella; beads of basal spiral cords progressively lower and more rounded toward umbilicus. Umbilicus closed in adults, but remaining open and steep-sided in juveniles, its edge marked by the sixth basal spiral cord. Peristome markedly oblique, almost tangential; aperture subcircular to D-shaped, flattened parietally; columella pillar well developed, protruding slightly into aperture, a strong, peg-like tooth at its base and a low bulge above its mid region; interior of outer lip subterminally thickened and set with 8-10 elongate denticles which extend into aperture as in-running ridges; that nearest columella larger, a deep U-shaped notch separating it from basal columella tooth; outer portion of lip flaring and bearing additional secondary granules and wrinkles distal to primary denticles; these continue around reflected portion of columella lip; parietal region covered with glossy callus bearing superficial wrinkle-like ridges; callus not extending beyond limit of peristome; interior of aperture nacreous.

Microsculpture (Fig. 27B, C): Juvenile shell with vermiform spiral threads, these continue throughout shell, becoming oblique on last adult whorl (cf. Ascetostoma providentiae); the scratch-like adult microsculpture of other species is not evident.

Protoconch (Fig. 27A, C): Greyish white, more or less level with first teleoconch whorl or at most weakly exsert; diameter ca 270 um; terminal lip distinct, shallowly convex; superficial sculpture well developed, irregular and wavy, with a predominant axial alignment; no spiral component evident.

Colour: Fresh specimens translucent white with regular reddish spotting, mostly on the spiral cords and usually in more or less axially aligned rows; final portion of last adult whorl washed with pale orange-brown; some evidence of a dirty white intritacalx deposit remaining in sculptural interstices of fresh specimens.

Dimensions: Holotype (largest specimen), length 3.07 mm, diameter 2.93 mm.

Operculum, radula and external anatomy: Unknown.

Holotype (Fig. 26A-D): KENYA: Kilifi (3.60236[degrees]S 39.81190[degrees]E), lagoon inshore of coral reef, ca -4 m, in sand from base of coral outcrops, 20.xii.1991, D. Herbert (NMSA K7929/T2640).

Paratypes: Same data as holotype (NMSA L8270/T2641, 15 specimens; MNHN 24650, 1 specimen; NHMUK 20110383, 1 specimen). MOZAMBIQUE: Pemba (12.937[degrees]S 40.521[degrees]E), Praia do Uimbe, living amongst dead coral in shallow subtidal, J. Rosado, xi.2010 (J. Rosado coll'n).

Distribution and habitat (Fig. 28): Known only from the coast of central Kenya and northern Mozambique, evidently in shallow subtidal habitats associated with fringing reef systems.

Remarks: Amongst the regional fauna, H. serratocinctum most closely resembles the Mascarene H. stictum (see below), particularly in terms of size, coloration and apertural dentition. The less elevated spire, more angular sculpture and strong, saw-toothed peripheral cord of H. serratocinctum, however, are distinctive. There is also some similarity with H. fimbriatum (Pease, 1861) (Fig. 69C, D), reportedly from Hawaii (but see Kay 1979), and H. corallinum Jansen, 1994 from the Great Barrier Reef, but in both these species the columella has a weaker basal tooth and lacks a low bulge above this.

They also have fewer spiral cords on the penultimate whorl (four) and a flatter base giving a more trochiform profile.

Herpetopoma (s.s.) seychellarum (G. & H. Nevill, 1869) comb. n. Fig. 29

Euchelus seychellarum: G. & H. Nevill 1869: 157, pl. xvii, fig. 107; Pilsbry 1890 in 1889-90: 438, pl. 57, fig. 13. Type loc.: Island of Mahe, Seychelles.

Type material: Five syntypes of Euchelus seychellarum G. & H. Nevill, 1869, in the Indian Museum, Kolkata (M13143/2), one is here figured and designated lectotype.

Remarks: This species does not appear to have been recorded subsequent to the original description. Its small size (diameter 2.8 mm), depressed profile and wide umbilicus, together with the distinct, peg-like basal columella tooth and dentate interior of the outer lip render it easily separable from other south-western Indian Ocean chilodontids. Obviously such small species are easily overlooked, but the evident absence of additional material from the Seychelles raises the possibility that the original material was mislocalised. Comparison with taxa from other areas may shed further light on this subject. The Philippine H. exasperatum (A. Adams, 1853) has a similarly depressed shape, but is larger (diameter attaining 6.5 mm) and has spiral cords of alternating size and crisper sculpture (Fig. 68E, F).

Herpetopoma (s.s.) stictum sp. n. Figs 28, 30, 31

Euchelus gemmatus [non Gould, 1845]: Jay 2009.

Etymology: From Greek stiktos (spotted); in reference to the colour pattern. Description:

Shell: Small, trochoid-turbiniform, relatively solid; length slightly exceeding diameter (L/D=1.07-1.19); teleoconch of approx. 4.5 whorls; spire whorls rather flat-sided, last adult whorl rounded, but slightly flatter below periphery; suture indented, level with subperipheral spiral cord, but descending below this immediately prior to aperture in fully mature individuals; first teleoconch whorl initially sculptured only with axial pliculae (ca 20); 2 spiral cords arising in latter half of whorl, a third arising beneath adapical suture during second whorl, a fourth arising below subsutural cord during third whorl; end of penultimate whorl with 4 spiral cords of more or less equal strength above abapical suture; cords equal to or slightly narrower than their intervals and crossed by prosocline axial pliculae; pliculae slightly narrower than spiral cords, the latter with roundly angular beads where crossed by pliculae, those on subsutural and peripheral cords slightly stronger (ca 30 on peripheral cord of last adult whorl); interstices roundly quadrate. Base with 5 spiral cords, the outer (subperipheral) one strongest and with roundly angular beads, the others progressively with lower, more rounded beads; a weak sixth cord bordering umbilicus; cords slightly wider than their intervals. Umbilicus open in juveniles and subadults, steep-sided, occasionally remaining narrowly patent even at maturity, but generally occluded by reflected columella lip and if evident at all then only as a shallow depression. Peristome markedly oblique, almost tangential; aperture D-shaped, somewhat flattened parietally; columella pillar well developed, a little oblique and protruding slightly into aperture; a distinct, peg-like tooth at its base with a second low bulge sometimes evident above this; interior of outer lip thickened and set with 7 or 8 primary denticles which extend into aperture as in-running ridges; that nearest columella larger, a deep U-shaped notch separating it from basal columella tooth; outer portion of lip flaring and bearing additional secondary granules and wrinkles external to primary denticles; these continue around reflected portion of columella lip, one particularly strong secondary granule near base of basal columella notch; parietal callus not extending beyond limit of peristome, sometimes with traces of superficial wrinkle-like ridges; interior of aperture nacreous.

Microsculpture (Fig. 31B, C): Apical whorls with vermiform spiral threads; weak scratch-like sculpture developing subsequently, but retaining traces of vermiform threads on spiral cords; interstices with sparse microscopic granules.

Protoconch (Fig. 31A, C): Translucent whitish in fresh specimens, last quarter whorl and initial half of first teleoconch whorl mauve-brown; more or less level with early part of first teleoconch whorl, its apex slightly down-tilted; diameter 250-280 um; terminal lip weakly convex; superficial sculpture well developed, irregular and wavy, with a predominant axial alignment; no spiral component evident.

Colour: Whitish with sparse, mauve-brown spots on spiral cords; spots sometimes aligned into diffuse axial bands on last adult whorl; base with fewer spots, generally more uniform white; spots fading to pinkish brown in old or worn specimens; fresh examples with a thin, dirty-buff, chalky intritacalx deposit.

Dimensions: Holotype, length 4.9 mm, diameter 4.25 mm; length variation of mature specimens 3.3-5.3 mm.

Operculum, radula and external anatomy: Unknown.

Holotype (Fig. 30): REUNION: not further localised (M. Jay coll'n, MNHN 24651).

Paratypes: REUNION: same as holotype (M. Jay coll'n, MNHN 24652, 12 specimens). MAURITIUS: off Troux aux Biches (20.0325[degrees]S 57.5411[degrees]E), reef front, ca -5 m, fine sand, D. Herbert, ix.1991 (NMSA K8309/T2757, 1 specimen); ditto (20.0325[degrees]S 57.5408[degrees]E), reef front, ca-10 m, fine sand, D. Herbert, ix.1991 (NMSA K8593/T2739, 11 specimens); Riambel lagoon (20.5206[degrees]S 57.4883[degrees]E), beach-drift, R. Kilburn & D. Herbert, ix.1991 (NMSA K7767/T2755, 45 specimens, K7771/T2756, 5 specimens); Gris Gris (20.5243[degrees]S 57.5239[degrees]E), debris on surf beach opposite reef-break, R. Kilburn & D. Herbert, ix.1991 (NMSA K8294/ TT2753, 1 specimen, K9324/T2754, 10 specimens).

Additional material examined (all NMSA): MAURITIUS: Pointe Radeau, south of Roches Noires (20.1287[degrees]S 57.7573 E), shell debris near reef gap, R. Kilburn & D. Herbert, ix.1991 (K9587); Tamarin Bay (20.3264[degrees]S 57.3775[degrees]E), beach-drift, R. Kilburn & D. Herbert, ix.1991 (K8497); Souillac, lagoon below cliffs west of Gris Gris (20.525854[degrees]S 57.527375[degrees]E), living, in washings from algae and dead coral blocks, D. Herbert, 14.ii.2011 (L8356, L8402 living juvenile). RODRIGUES: Between Anse aux Anglais and Pointe Venus (19.6752[degrees]S 63.4313[degrees]E), beach-drift, D. Herbert, ix.1991 (K7795); Anse aux Anglais (19.6716[degrees]S 63.4334[degrees]E), reef crest and platier necrose, exposed at LT, D. Herbert, ix.1991 (K8672); Grand Baie (19.67175[degrees]S 63.45089[degrees]E), beach-drift near stream, D. Herbert, ix.1991 (K9162).

Distribution and habitat (Fig. 28): Known only from the Mascarene Islands. Dead shells are moderately common in beach-drift samples, but living material has rarely been found. Jay (2009) reported it (as Euchelus gemmatus) as 'living under stones at 10-15 m. Rare' in Reunion, and I obtained a single live-taken juvenile from algal and coral washings collected at LST on the reef crest at Souillac, Mauritius.

Remarks: With its spotted colour pattern, Herpetopoma stictum resembles H. serratocinctum, however, the present species attains a larger size (max. length 5.3 vs 3.1 mm), and has a less globose, more trochiform profile. In addition, H. serratocinctum has sharper sculpture, with spiral cords of alternating size and a saw-toothed peripheral cord. H. howensis Jansen, 1994 from Lord Howe Is. is also spotted, but has a less elevated spire, a weaker basal columella tooth and has intermediary spiral threads between the primary spiral cords.

The Hawaiian H. corrugatum (Pease, 1861) has a more roundly beaded sculpture, a weaker basal columella tooth, a less obviously spotted colour pattern and commonly retains an open umbilicus (Fig. 69A, B). H. fimbriatum (Pease, 1861), also reportedly from Hawaii, has a more angular periphery and only three spiral cords on the penultimate whorl, and lacks a spotted colour pattern (Fig. 69C, D). Jay (2009) confused the present species with another Pacific species, H. gemmatum (Gould, 1845), but that species has more rounded whorls, a more finely beaded sculpture and a clearly patent umbilicus. (NB: The shell figured by Johnson (1964: pl. 15, fig. 10) as the lectotype of Trochus (Monodonta) gemmatus Gould, 1845, with a diameter of 20 mm cannot in fact be the genuine lectotype.) Diloma verruca Gould, 1861, a very poorly documented species from Chinese waters, also belongs within this group of Herpetopoma species, but has two widely spaced primary spiral cords at and just above the periphery of the last adult whorl (Fig. 69E, F).

Herpetopoma (s.l.) helix (Barnard, 1964) comb. n. Figs 4I, 32-34

Turcica helix: Barnard 1964: 21, fig. 3e; Kensley 1973: 44, fig. 110. Type loc.: off Cape Vidal, KZN, South Africa, 80-100 fath. [-146-183 m].

Description:

Shell: Turbiniform (L/D=1.10-1.25), teleoconch of 4-5 whorls; whorls rounded, sutures indented and inserted at level of subperipheral cord; first teleoconch whorl with 14-16 axial pliculae; second and subsequent whorls with axial pliculae and relatively strong spiral cords, 2 on second whorl, 3 on subsequent ones; cords bearing axially elongate beads where crossed by pliculae; last adult whorl with 40-50 axial pliculae and 3 spiral cords above and including periphery, occasional specimens with weaker intermediaries; intervals between cords equal to or wider than cords themselves and rendered obliquely cancellate by axial pliculae; interval between second and third cords frequently wider than others. Base with 4-5 somewhat less well developed spiral cords, sometimes with a sixth close to columella; axial pliculae of base progressively less elevated toward shell axis and cords thus less obviously granular. Umbilicus lacking in adult specimens, but sometimes evident as a narrow chink in juveniles; umbilical region usually at least partially covered by parietal/columella callus. Peristome oblique; aperture subcircular, flattened at paries; columella with a single simple tooth at its base; interior of outer lip thickened, bearing approx. 12 ridge-like denticles, one where basal portion of lip joins columella frequently larger, with a shallow notch separating it from columella tooth; an additional small granule is usually present just external to this notch; exterior of outer lip thickened subterminally but not distinctly varixed; interior nacreous, deeper region lacking in-running ridges, but cords of outer surface showing through.

Microsculpture (Fig. 33A-C): Vermiform spiral threads not evident on apical whorls; microsculpture between axial pliculae instead comprising numerous crisp granules, frequently connected by thread-like axial elements; adult microsculpture similar but rather more irregular and often completely obscured by thick intritacalx deposit.

Protoconch (Fig. 33C): Translucent white; diameter 260-280 um; moderately exsert and relatively globose; worn in all available material; terminal lip shallowly convex; superficial sculpture mostly eroded, but with traces of granulation remaining near suture.

Colour: Shell evidently more or less uniformly greyish white to yellowish white and somewhat translucent; intritacalx deposit usually yellowish white to buff-brown, but some specimens patterned with broad bands in shades of brownish grey.

Dimensions: Largest NMSA specimen length 4.0 mm, diameter 3.4 mm.

Operculum (Fig. 4I): Relatively tightly multispiral throughout.

Radula (Fig. 33D, E): Formula [infinity]+4+1+4+[infinity]; ca 40 transverse

rows of teeth; transition from lateral to marginal series not well defined, the fourth lateral could also be interpreted as a marginal. Rachidian with broad, trigonal cusp and well-developed hood, but lacking a distinct transverse basal ridge and near-basal medial indentation; cutting edge with a very long, acuminate, central denticle and 2 or 3 smaller, likewise elongate denticles on each side. Lateral teeth progressively decreasing in size from first to last, but not markedly so, their cusps obliquely trigonal with coarse lateral denticles on both margins (3-5). Marginals closely resembling those of H. scabriusculum, but a little more elongate; cusps of inner marginals with well-developed pectinate outer margin; outermost marginals shorter and with a somewhat dilated, fringed cusp.

External anatomy: Evidently chilodontid, but material insufficiently well preserved to provide meaningful detail.

Type material: SOUTH AFRICA: KwaZulu-Natal: Holotype of Turcica helix Barnard, 1964 (SAMC) off Cape Vidal (Zululand), 80-100 fath. [-146-183 m] (A9295), and one paratype, off Umkomaas, 40 fath. [-73 m] (A9256, broken).

Material examined (all NMSA unless indicated otherwise): MADAGASCAR: Secteur de Manantenina (24.3833[degrees]S 47.5330[degrees]E), -158-168 m, dredged Nosy Be 11, Exped'n Atimo Vatae, st'n DW3522, 1.v.2010 (MNHN); ditto, (24.3833[degrees]S 47.5170[degrees]E), -200-220 m, dredged Nosy Be 11, Exped'n Atimo Vatae, st'n DW3523, 1.v.2010 (MNHN). MOZAMBIQUE: Inhambane transect, Campagne Mainbaza, RV Vizconde de Eza, dredged, st'n CP3144 (23.550[degrees]S 35.683[degrees]E), living, -171-180 m, 11.iv.2009 (MNHN); Maputo transect, Campagne Mainbaza, RV Vizconde de Eza, dredged, st'n CP3130 (25.883[degrees]S 33.117[degrees]E), living, -112-127 m, 9.iv.2009 (MNHN); ditto, st'n CP3131 (25.933[degrees]S 33.117[degrees]E), -193-194 m, 9.iv.2009 (MNHN); off Ponta Techobanine (26.68132[degrees]S 32.95093[degrees]E), -100-135 m, dredged J. Rosado, xii.2005 and i.2010 (D. Slater coll'n). SOUTH AFRICA: KwaZulu-Natal: off Boteler Point (27.0133[degrees]S 32.9183[degrees]E), -70 m, some coarse sand, some shell rubble, dredged NMDP, RV Meiring Naude, st'n ZB4, 6.vi.1987 (D7412); off Dog Point (27.1083[degrees]S 32.8817[degrees]E), living, -70 m, sandstone conglomerate, dredged NMDP, R. V. Meiring Naude, St'n ZC3, 4.vi.1987 (E1740); Sodwana Bay (27.533[degrees]S 32.683[degrees]E), -100 m, dredged, CSIR Water Research (A5793); off Gipsy Hill (27.8117[degrees]S 32.6570[degrees]E), -100-125 m, broken shell, dredged NMDP, RV Meiring Naude, st'n ZK9, 11.vi.1988 (E3247); NE of Leven Point (27.9167[degrees]S 32.6467[degrees]E), -250 m, coarse sand, dredged NMDP, RV Meiring Naude, st'n ZL5, 9.vi.1988 (S1143); SE of Cape Vidal (28.1183[degrees]S 32.6100[degrees]E), living, -145 m, medium sand, dredged NMDP, RV Meiring Naude, st'n ZM7, 10.vi.1988 (E7514); ditto (28.1400[degrees]S 32.6067[degrees]E), -165 m, moderately fine sand, dredged NMDP, RV Meiring Naude, st'n ZM8, 11.vi.1988 (E7599); off Mission Rocks (28.2917[degrees]S 32.5700[degrees]E), -100 m, medium sand, dredged NMDP, RV Meiring Naude, st'n ZN7, 11.vi.1988 (E3828); SE of Neill Peak [Cunge Hill] (28.7400[degrees]S 32.5367[degrees]E), -320-340 m, sandy mud, dredged NMDP, RV Meiring Naude, st'n ZP5, 12.vi.1988 (E3976); Port Durnford-Richard's Bay (29.0067[degrees]S 32.2000[degrees]E), -152 m, mud and stones, dredged NMDP, RV Meiring Naude, st'n ZQ7, 13.vi.1988 (V3920); SE of Port Durnford (29.0150[degrees]S 32.2017[degrees]E), -215 m, glutinous sandy mud, dredged NMDP, RV Meiring Naude, st'n ZQ8, 13.vi.1988 (E3118); off Sheffield Beach (29.6442[degrees]S 31.4783[degrees]E), -110 m, muddy sand, dredged NMDP, RV Meiring Naude, st'n ZU14, 19.vi.1989 (E9446); SE of Green Point (30.250[degrees]S 30.905[degrees]E), living, -100 m, fine sand, rubble, dredged NMDP, RV Meiring Naude, st'n XX92, 8.vii.1986 (D5990); off Umzinto (30.3600[degrees]S 30.8500[degrees]E), living, -84 m, dredged NMDP, RV Meiring Naude, st'n X2, 15 vii.1982 (D5427); off Park Rynie (30.375[degrees]S 30.855[degrees]E), -100 m, sand & sponge rubble, dredged NMDP, RV Meiring Naude, 04.iii.1981 (B3717); off Mtamvuna River (31.1650[degrees]S 30.2516[degrees]E), living, -140 m, sponge rubble, dredged NMDP, RV Meiring Naude, st'n A6, 18.viii.1981 (E224). Eastern Cape: off Port Grosvenor (31.41[degrees]S 29.95[degrees]E), -80 m, worn coral nodules, dredged NMDP, RV Meiring Naude, st'n D17, 16.viii.1981 (E176); ditto (31.4360[degrees]S 29.9516[degrees]E), -100-115 m, sand, some mud, solitary coral, shells, dredged NMDP, RV Meiring Naude, st'n D3, viii.1981 (C1338); off Mgazi River (31.7450[degrees]S 29.5617[degrees]E), -180 m, soft mud, dredged NMDP, RV Meiring Naude, st'n J1, 15.vii.1982 (E281, E7540); off Shixini Point (32.5267[degrees]S 28.8833[degrees]E), -500 m, muddy sand, coral rubble, dredged NMDP, RV Meiring Naude, st'n T17, 13.vii.1984 (V2789, shells very old).

Distribution and habitat (Fig. 34): Southern Madagascar and south-eastern Africa, from southern Mozambique (Inhambane area) to the central Transkei region, Eastern Cape, South Africa (Shixini Point); -70-500 m, living specimens -70-180 m, on varied hard substrata.

Remarks: Relatively little fresh material of this species is available considering the amount of dredging that has been done between -50-200 m off KwaZulu-Natal and the Transkei region of Eastern Cape. Its small size, rounded whorls and strong spiral sculpture render it easily separable from other local chilodontid taxa. There is some resemblance to H. ?naokoae (below), but H. helix has fewer spiral cords above the suture (three compared with four in H. ?naokoae) and the cords are stronger. The relatively smooth, globose protoconch, granular microsculpture and weak basal columella tooth place this species apart from Herpetopoma (s.s.).

Herpetopoma (s.l.) ?naokoae Poppe, Tagaro & Dekker, 2006 Figs 35, 36

Herpetopoma naokoae: Poppe et al. 2006: 37, pl. 10, figs 1, 3. Type loc.: Punta Engano, Mactan Is., Philippines.

Material examined: REUNION: off Ste-Marie (20.85[degrees]S 55.60[degrees]E), -280-340 m, Marion-Dufresne 32, st'n DC128, dredged, 1982; ditto (20.85[degrees]S 55.62[degrees]E), -345-375 m, Marion-Dufresne 32, st'n DS131, dredged, 1982 (MNHN). SOUTH AFRICA: KwaZulu-Natal: off Neill Peak [Cunge Hill, 28.7400[degrees]S 32.5367[degrees]E], -320-340 m, sandy mud, dredged NMDP, RV Meiring Naude, st'n ZP5, 12.vi.1988 (NMSA E6967).

Remarks: A small number of specimens closely resembling the Philippine H. naokoae have been dredged in the south-western Indian Ocean, off Reunion (MNHN) and Zululand (NMDP). Although extremely similar to H. naokoae, they have a less rounded apex and I am uncertain whether they are genuinely conspecific with that species. In the absence of more material, I can only identify them as H. ?naokoae. No specimens have been taken alive in the south-western Indian Ocean, but one is fresh and shows the characteristic dirty buff and grey intritacalx deposit typical of many chilodontids. All others are uniform off-white. The protoconch is translucent white, globose and exsert, with a diameter of ca 285 um; in the material available the surface is worn and sculptural detail not evident. The apical whorls of the teleoconch have a microsculpture of vermiform spiral threads that become more oblique and fragmented with growth, the adult microsculpture comprising a fine, irregular granulation.

Herpetopoma pruinosum (Marshall, 1979), from the Kermadec Ridge, is also similar but has a lower spire and a finer, more obviously cancellate sculpture. Additional similar, but more elongate specimens have been sorted from some of the same dredge samples collected off Reunion and are discussed below (see H. xeniolum).

Herpetopoma (s.l.) xeniolum (Melvill, 1918) comb. n. Figs 36-38

Euchelus xeniolum: Melvill 1918: 154, pl. 5, fig. 27. Type loc.: Chabar, Gulf of Oman [= Chah Bahar, Iran], 5 fath. [-9 m] (Townsend).

Turcica (Perrinia) waiwailevensis: Ladd 1982: 23, pl. 24, figs 10-13. Type loc.: Station C2026, Viti Levu, Fiji; Pliocene. Syn. n.

Herpetopoma eboreum: Vilvens & Heros 2003: 61, figs 1-4; Poppe et al. 2006: 36, pl. 10, fig. 2; Poppe & Tagaro 2008: 174, pl. 32, fig. 1. Type loc.: Touho Pass, Touho area, New Caledonia, -50-62 m. Syn. n.

Euchelus townsendianus [non Melvill & Standen, 1903]: Jay 2009.

Type material: Holotype of Euchelus xeniolum Melvill, 1918 in NHMUK (1921.1.28.30); Trew (1987) was in error in stating that there were three specimens registered. Holotype of Turcica (Perrinia) waiwailevensis Ladd, 1982 in USNM (2501420). Holotype of Herpetopoma eboreum Vilvens & Heros, 2003 in MNHN.

Other material examined (all MNHN): REUNION: off Ste-Marie (20.867[degrees]S 55.633[degrees]E), -110 m, MarionDufresne 32, st'n DC126, dredged, 1982; off St-Joseph (21.383[degrees]S 55.617[degrees]E), -205-215 m, Marion-Dufresne 32, st'n DR47, dredged, 1982; Reunion, not further localised (M. Jay coll'n). MADAGASCAR: West of Nosy Be (13.450[degrees]S 47.917[degrees]E), -187-247 m, Campagne Miriky, st'n DW3234, dredged, 3.vii.2009.

Remarks: A number of samples collected off Reunion are evidently referable this species, which I consider is closer to Herpetopoma than to Euchelus on account of its small size and the U-shaped notch at the columella base (albeit relatively weak). The species is poorly known and has not to my knowledge been recorded subsequent to the original description. The holotype (Fig. 37A, B) has four granular spiral cords on the penultimate whorl as do some Reunion specimens (Fig. 37C, D). However, other specimens in the Reunion samples have five such cords (Fig. 37E, F) and closely resemble the holotype of Turcica (Perrinia) waiwailevensis Ladd, 1982 from the Pliocene of Fiji (Fig. 37G, H). I have no doubt that the Reunion samples belong to a single species and consider the number of spiral cords on the penultimate whorl (four or five) to be a variable character. There is evidently similar variation in the number of spiral cords on the base (6-8). As a consequence, I can find no substantive differences by which to separate Herpetopoma waiwailevensis from H. xeniolum. In addition, H. eboreum Vilvens & Heros, 2003, described from shallow water off New Caledonia and recorded also from deeper water off the Philippines (Poppe et al. 2006), appears indistinguishable from H. waiwailevensis. I believe that all three names refer to a single widespread species, for which H. xeniolum is the earliest name. Euchelus hummelincki Moolenbeek & Faber, 1989 from the Caribbean is another similar species, but is evidently smaller (length up to 3.2 mm) and has somewhat coarser sculpture.

The holotype of H. xeniolum was collected in shallow water (-9 m) and similarly the overall facies of the fauna at the type locality of H. waiwailevensis is that of a shallowwater, lagoonal system (Ladd 1966, 1982). The depth at which the dredged material from Reunion was obtained (-110-340 m) would thus seem to be anomalous. However, Reunion has a steeply shelving sublittoral zone and dead specimens of typically shallowwater species are frequently found at greater depths. That the species is also present in the M. Jay collection (MNHN) suggests that it does indeed occur in relatively shallow water around Reunion. The same may also apply to some rather worn specimens from off the steeply shelving coast of Nosy Be, which I also tentatively identify as H. xeniolum.

This material resembles H. Inaokoae (above), but the whorls are less convex and the shell is consistently more elevated, L/D usually >1.23, spire height/aperture height usually >1.60 in H. xeniolum (usually <1.23 and <1.60 respectively in H. Inaokoae). Additionally, in H. Inaokoae the sculpture is coarser and the denticles inside the outer lip, although ridge-like, are restricted to the thickened region just inside the lip edge. In H. xeniolum some of these ridges extend deeply into the aperture. Furthermore, in the local H. Inaokoae specimens there is an additional small denticle adjacent to the notch between the two larger denticles at the junction of the base and columella, this is not present in the H. xeniolum material examined.

The protoconch is translucent white with a diameter of ca 220 um; its surface is eroded in the material available. A microsculpture of irregular vermiform spiral threads is present on the early teleoconch whorls; subsequent whorls with weak oblique vermiform threads and traces of very fine scratch-like marks.

Genus Vaceuchelus Iredale, 1929

Vaceuchelus: Iredale 1929: 272. Type species: Euchelus angulatus Pease, 1868 [= Monodonta foveolata A. Adams, 1853], by monotypy.

The shell of Vaceuchelus species is small (length <10 mm), predominantly white and has a cancellate or foveolate sculpture. The aperture lacks a well-developed, peg-like tooth and U-shaped notch at the base of the columella, and may or may not possess denticles inside the outer lip.

Iredale (1929) proposed the genus for Euchelus angulatus Pease, 1868 from the Tuamotu Archipelago, noting that it typified a large series of taxa which differed from more typical Euchelus-like species primarily in lacking a tooth at the base of the columella. It is certainly true that Vaceuchelus species lack the distinctive basal columella dentition of some chilodontid genera, but a number of species still retain some form of apertural dentition. Two subgroupings are evident, namely those which possess denticles inside the outer lip and those that do not. The type species, together with V. foveolatus (A. Adams, 1853), V scrobiculatus (Souverbie in Souverbie & Montrouzier, 1866) and V semilugubris (Deshayes, 1863) possess labral denticles, whilst others, e.g. V. cavernosus (Sowerby, 1905), V. clathratus (A. Adams, 1853), V. favosus (Melvill & Standen, 1896), V. gemmula (Turton, 1932), V. jayorum sp. n. and V. natalensis (Smith, 1906), seem to lack all traces of apertural dentition.

To provide a new genus-rank name for such denticle-less taxa would be premature at this stage, since the distinction is based on one character only and, furthermore, there are additional taxa, e.g. V. cretaceus (see below), which present a third, somewhat intermediate facies. Until such time as the data set available allows a more meaningful assessment, I employ Vaceuchelus in its widest sense. Differences in operculum form and protoconch morphology, such as the presence or absence of a sinusigera lip, are also evident, but information is available for too few taxa.

V. angulatus is almost certainly a junior synonym of V. foveolatus (A. Adams, 1853), also from the Tuamotu Archipelago (Pilsbry 1890 in 1889-90). The holotype of the former is somewhat worn, but appears to be nothing more than an elevated and perhaps abnormal example of V. foveolatus in which the upper spiral cord is weakly developed (compare figs 72-73 and 74-75 in Herbert 1996).

Key to species of Vaceuchelus in the south-western Indian Ocean

1 Shell whitish, usually boldly marked with dark brown to black blotches semilugubris

--Shell more uniform in colour, whitish to dirty buff, occasionally with ashy-grey axial bands 2

2 Adult length up to 8.5 mm; columella with a broad, low, rounded swelling at its base cretaceus

--Small (adult length <5.0 mm); columella lacking a basal swelling 3

3 Base with 3 major spiral cords (sometimes a weaker 4th adjacent to columella); umbilicus closed in adult; protoconch diameter ca 340 [micro]m gemmula

--Base with 4 major spiral cords (sometimes with a weaker 5th spiralling into umbilicus); umbilicus open in adult, albeit narrow; protoconch 260-300 [micro]m 4

4 Final quarter of last adult whorl with intermediary spiral cords present above periphery jayorum

--No intermediary spiral cords present on last adult whorl natalensis

Vaceuchelus cretaceus sp. n. Figs 4J, 6F, 39-41

Euchelus scrobiculatus [non Souverbie, 1866]: Jay 2009.

Etymology: From Greek creta (white earth or chalk); in reference to the superficial chalk-like intritacalx deposit on the shell.

Description:

Shell: Small, but relatively large for genus; elevated-turbiniform (L/D=1.0-1.25); teleoconch of 4.5-5.0 whorls; sculpture initially strongly cancellate, becoming foveolate with growth; spire truncate and protoconch sunken; first teleoconch whorl initially sculptured only by rib-like axial pliculae, but 3 spiral cords develop soon thereafter, one forming shoulder, another level with the abapical suture and the third between these at whorl periphery; cords and pliculae thickening considerably during third whorl and becoming less well defined; intermediary cords absent, with the exception of a fourth cord which usually develops on shoulder during third teleoconch whorl; intervals between cords wider than cords themselves; cords and pliculae interact to produce low conical granules where they cross; last adult whorl with 15-20 pliculae, those behind outer lip usually poorly defined or obsolete; pliculae narrower than cords on early whorls, more or less equal to them on last adult whorl; interstices distinctly quadrate apically, but becoming more rounded and pit-like (foveolate) on last adult whorl; strong growth flaws frequently present on last adult whorl. Base with 3 spiral cords, one level with suture, one marking edge of umbilicus and another between these; interval between outer and middle cords usually broader and with only weakly developed pits, that between middle and inner cords narrower and more strongly pitted; an additional cord is evident within umbilicus of young juveniles, but this becomes obscured with growth; umbilicus usually narrowly patent even in adults, occasionally closed; relatively wider in juveniles. Peristome oblique; aperture subcircular; columella concave with a broad rounded swelling at its base; swelling non-nacreous and rather variable in size; interior of aperture nacreous when fresh, lacking ridges or denticles inside outer lip.

Microsculpture (Fig. 40B, C): Rather poorly defined and mostly covered by intritacalx deposit in fresh specimens; surface of apical whorls appearing etched, but with some traces of vermiform spiral threads; later whorls with close-set, shallow, prosocline, scratch-like marks.

Protoconch (Fig. 40C): White; diameter ca 200 um; sunken; apex very slightly pinched in; terminal lip with a well-developed trigonal projection; superficial sculpture well developed, arranged in irregular axial lines, spiral element scarcely evident.

Colour: Fresh specimens milky-white with a relatively thick, chalky, white to pale buff or ashy-grey intritacalx deposit; deposit usually somewhat eroded.

Dimensions: Holotype, length 7.6 mm, diameter 6.6 mm; largest specimen (NMSA S4006), length 8.65, diameter 6.9 mm.

Operculum (Fig. 4J): Initially tightly multispiral, but whorls broadening with growth and becoming more openly multispiral.

Radula (Fig. 40 D, E): Formula [infinity]+3+1+3+[infinity]; ca 45 transverse rows of teeth; transition from lateral to marginal series not well delineated. Rachidian with well-developed hood and narrowly trigonal cusp; cusp with small medial indentation near its base; cutting edge with a dominant, lanceolate central denticle, with 2 or 3 smaller denticles on each side. Only 3 lateral teeth evident, the fourth tooth is longer and lacks the robust, alate shaft of the laterals, and I consider it to be a marginal; lateral tooth cusps decreasing slightly in size from first to third, with a large, spathulate central element and smaller lateral denticles on both margins, those on the outer edge coarser. Marginals generally long and very slender, tending to collapse when air dried; inner ones somewhat shorter with a rather weakly and irregularly dentate, recurved cusp, and lacking well-developed pectinate denticles on its outer margin.

External anatomy (Fig. 6F): Head-foot largely white, cephalic and most epipodial tentacles blackish; some additional dark pigmentation on snout and lips, and on free margin of cephalic lappets (colour lost in alcohol). Cephalic lappets relatively broad, but not meeting in mid-line, free margin with fine projections; snout with well-developed lateral flanges; right post-ocular peduncle present; right subocular tentacle not evident; free margin of left neck lobe more extensively tentaculate than that of right one; approx. 10 epipodial tentacles of varying size on each side; an indistinct epipodial sense organ seemingly present at base of most epipodial tentacles. (Only one preserved specimen available; paratype, NMSA S4006/T2638.)

Holotype (Fig. 39A-C): SOUTH AFRICA: KwaZulu-Natal: off Boteler Point (27.00[degrees]S 32.92[degrees]E), -70 m, coral rubble, dredged NMDP, RV Meiring Naude, st'n ZB5, 6.vi.1987 (NMSA E1761/T2600).

Paratypes: REUNION: off St-Paul Bay, Marion-Dufresne 32, st'n DC85 (21[degrees]00'S 55[degrees]15'E), living, -58-70 m, dredged, 1982 (MNHN 24655, 54 specimens); Cap la Houssaye, hand-dredged sand, J. Drivas (NMSA K2756/T2603). SOUTH AFRICA: KwaZulu-Natal: SE of Kosi Bay (26.9000[degrees]S 32.9250[degrees]E), living, -50 m, coral slabs, dredged NMDP, RV Sardinops, st'n ZA37, 3.vi.1990 (NMSA S4006/T2638, 1 specimen); SE of Kosi River Mouth (26.9167[degrees]S 32.9300[degrees]E), -65 m, sponge, gorgonians, medium sand, dredged NMDP, RV Meiring Naude, st'n ZA12, 7.vi.1987 (NMSA D8017/T2602, 1 specimen); same data as holotype (NMSA V2961/T2639, 3 specimens; NHMUK 20110384, 1 specimen); off Boteler Point (27.0600[degrees]S 32.9083[degrees]E), -70 m, sand, some stones, dredged NMDP, RV Sardinops, st'n ZB24, 6.vi.1990 (NMSA S4157/T2601, 1 specimen); off Boteler Point (27.0133[degrees]S 32.9183[degrees]E), -70 m, some coarse sand, some shell rubble, dredged NMDP, RV Meiring Naude, st'n ZB4, 6.vi.1987 (NMSA D7420/T2636, 1 specimen); NE of Dog Point (27.0800[degrees]S 32.89167[degrees]E), -65 m, sand, lithothamnion pebbles, dredged NMDP, RV Sardinops, st'n ZC9, 7.vi.1990 (NMSA S7593/T2637, 4 specimens); off Rocktail Bay (27.1850[degrees]S 32.8483[degrees]E), -100 m, sand, dredged NMDP, RV Sardinops, st'n ZD4, 7.vi.1990 (NMSA S5138/T2602, 3 specimens); off Rocktail Bay (27.1900[degrees]S 32.8500[degrees]E), -100 m, sandstone rubble, dredged NMDP, RV Meiring Naude, st'n ZD1, 4.vi.1987 (NMSA D7598/T2604, 1 specimen); Sodwana Bay (27.5330[degrees]S 32.6830[degrees]E), -100 m, dredged CSIR Water Research (NMSA S9831/T2607, 1 specimen); SE of Mission Rocks (28.2917[degrees]S 32.5433[degrees]E), -50 m, old coral rubble, lithothamnion, dredged NMDP, RV Meiring Naude, st'n ZN1, 10.vi.1988 (NMSA E4641/T2605, 1 specimen; E7491/T2608, 3 specimens).

Additional material examined (all NMSA unless indicated otherwise): REUNION: off south-east coast of island, Marion-Dufresne 32, st'n DC1 (21[degrees]13'S 55[degrees]49'E), -150-160 m, dredged, 1982 (MNHN); Reunion, not further localised (M. Jay coll'n, MNHN). MOZAMBIQUE: off Lacerda Lighthouse (25.56167[degrees]S 32.84472[degrees]E), -52-55 m, dredged, vi.2010, (J. Rosado coll'n); off Inhaca Is. (26.020[degrees]S 33.066[degrees]E), -125 m, dredged J. Rosado, ii.2006 (D. Slater coll'n); off Ponta Techobanine (26.68132[degrees]S 32.95093[degrees]E), -60-135 m, dredged J. Rosado, xii.2005 and i.2010 (D. Slater coll'n). SOUTH AFRICA: KwaZulu -Natal: off Kosi Bay (26.8916[degrees]S 32.9266[degrees]E), -51 m, sand, stones large algae, dredged NMDP, RV Sardinops, st'n ZA48, 4. vi.1990 (S4061); off Boteler Point (27.0067[degrees]S 32.9083[degrees]E), -51 m, sand, some lithothamnion pebbles, dredged NMDP, RV Sardinops, st'n ZB9, 5.vi.1990 (S9668); ditto (27.0083[degrees]S 32.9117[degrees]E), -50 m, dead coral rubble and lithothamnion, dredged NMDP, RV Meiring Naude, st'n ZB7, 6.vi.1987 (E5263); ditto (27.0117[degrees]S 32.9200[degrees]E), -70 m, rocks, sand, dredged NMDP, RV Sardinops, st'n ZB19, 6.vi.1990 (S8701); ditto (27.0200[degrees]S 32.9183[degrees]E), -76 m, lithothamnion pebbles, sand, dredged NMDP, RV Sardinops, st'n ZB15, 5. vi.1990 (S7550); NE of Dog Point (27.0800[degrees]S 32.8867[degrees]E), -56-57 m, sand, lithothamnion pebbles, dredged NMDP, RV Sardinops, st'n ZC8, 6.vi.1990 (S5052); SE of Rocktail Bay (27.2017[degrees]S 32.8300[degrees]E), -60 m, coarse sand, dredged NMDP, RV Sardinops, st'n ZD9, 8.vi.1990 (V875); off Sodwana Bay (27.5300[degrees]S 32.7133[degrees]E), -70 m, dead coral rubble, dredged NMDP, RV Sardinops, st'n ZH18, 2.vi.1990 (S4564); ditto (27.4781[degrees]S 32.7232[degrees]E), -46 m, sediment at base of drop-off in canyon, dredged UND, Marine Geoscience Unit, 7.xi.1992 (V2609); NE of Liefeldt's Rocks (27.7200[degrees]S 32.6617[degrees]E), -50 m, lithothamnion, stones, some coarse sand, dredged NMDP, RV Meiring Naude, st'n ZJ1, 8.vi.1988 (E4343); Leadsman Shoal (27.8000[degrees]S 32.6160[degrees]E), -100 m, dredged A.D. Connell, iv.1980 (B4066); off Leven Point (27.9167[degrees]S:32.6467[degrees]E), -250 m, coarse sand, dredged NMDP, RV Meiring Naude, st'n ZL5D, 9.vi.1988 (S9427).

Distribution and habitat (Fig. 41): South-western Indian Ocean, known only from Reunion, southern Mozambique and northern Zululand (south to Mission Rocks); shallow subtidal to -250 m, but mostly shallower than -160 m (living specimens -50-70 m); dead shells not uncommon amongst lithothamnion encrusted pebbles and coral rubble in -50-70 m, beyond the near-shore reef system in northern Zululand.

Remarks: There is no similar species yet reported from the south-western Indian Ocean. V. gemmula, V. jayorum and V. natalensis are much smaller and thinner shelled, lack a basal columella swelling and retain sharply defined spirals and axials throughout. Although they may resemble juvenile V. cretaceus, they have a narrower umbilicus, more evenly spaced cords on the base and a less strongly truncated apex. Furthermore, in these small species the spiral cords are stronger in relation to the axial pliculae and more elevated than they are in V. cretaceus. V. semilugubris is also smaller than V. cretaceus, has denticles inside the outer lip when fully mature and is typically patterned with bold black markings.

This species differs from V. angulatus (Pease, 1868) (type species of Vaceuchelus) and similar species from the south-western Pacific, such as V. foveolatus (A. Adams, 1853) and V. scrobiculatus (Souverbie in Souverbie & Montrouzier, 1866), in being larger and in lacking denticles or ridges inside the outer lip (cf. figures provided by Herbert 1996). More similar to V. cretaceus are V. cavernosus (Sowerby, 1905) from Sri Lanka (Fig. 70A, B) and V. clathratus (A. Adams, 1853) from the Philippines (Fig. 70C, D), both of which are of similar size and also lack sculpture inside the outer lip. Nonetheless, they retain a well defined, relatively fine, cancellate sculpture on the last adult whorl and have four and five spiral cords respectively on the base (including that level with suture) as opposed to three in V. cretaceus. Neither possesses the basal columella swelling of V. cretaceus. The most similar species is the recently described Vaceuchelus pagoboorum Poppe, Tagaro & Dekker, 2006 from the Philippines. This is clearly closely related to V. cretaceus and likewise possesses a broad swelling at the base of the columella, but differs in having an additional low rounded tubercle inside the outer lip near its junction with the parietal portion of the aperture, has more evenly spaced basal cords (four in juveniles compared with three in V. cretaceus, but the inner one becomes obsolete in adults), retains distinct pits in the interval between the outer and middle basal cords, and frequently has brownish markings on the spiral cords. With no material from intermediate localities, it is difficult to assess the significance of these differences, but they seem to constitute characters by which the populations can be distinguished and I thus describe the south-western Indian Ocean material as a new species.

I refer this species to Vaceuchelus with some hesitation. The overall facies of its shell also shows some resemblance to that of Trochus clathratus Aradas, 1847, type species of Putzeysia Sulliotti, 1889. In that genus, however, the apex is not flattened, and the protoconch is globose and less strongly sculptured (Engl & Rolan 2009). The protoconch of V. cretaceus is closer to that of V. natalensis and V. gemmula, but differs in having a distinct projection on the terminal lip. Furthermore, whereas the radula of V. natalensis appears to be simply a reduced version of the Herpetopoma radula, that of V. cretaceus differs in having a narrower, acutely trigonal rachidian cusp and inner marginals that lack a strongly pectinate outer margin. With no comparable information available concerning the type species of Vaceuchelus, these differences are difficult to evaluate, but they suggest a degree of intrageneric variability within Vaceuchelus that merits further study.

Vaceuchelus gemmula (Turton, 1932) comb. n. Figs 42-44

Euchelus gemmula: Turton 1932: 194, No 1347, pl. 49. Type loc.: Port Alfred, South Africa.

Euchelus natalensis: Bartsch 1915: 163; Turton 1932: 193, No 1346; Barnard 1951: 117, pl. xvi, fig. 16; 1963: 266 (in part).

Etymology: The species name gemmula, diminutive of Latin gemma (a bud or jewel) was formed as a feminine noun in apposition.

Description:

Shell: Small, turbiniform (L/D=0.90-1.15); teleoconch of up to 3.5 whorls; sculpture strongly cancellate; first whorl initially sculptured only with widely spaced, rib-like, axial pliculae (ca 15), but 3 spiral cords develop soon thereafter, one forming shoulder, another level with the abapical suture and the third between these at whorl periphery; cords persist and become progressively stronger with growth; an additional (fourth) subsutural cord may or may not develop on the shoulder during the last or penultimate whorl; no intermediary spiral cords; intervals between cords wider than cords themselves; last adult whorl with 20-30 axial pliculae; pliculae narrower than cords and somewhat lamellate, sometimes raised into squamose nodules where they cross cords; interstices obliquely quadrate. Base with 3 spiral cords, including that level with suture, usually with a weaker, rather ill-defined, fourth one present adjacent to columella; umbilicus closed or at most chink-like in adult, more obviously patent in some juveniles. Peristome oblique, aperture subcircular; columella concave, lacking dentition; outer lip notched at ends of spiral cords in juveniles and subadults, but less so in the largest specimens, when growth has ceased; even in the most mature specimens the outer lip is not conspicuously thickened and there is no trace of apertural teeth; interior nacreous and smooth, save for weak angles beneath external cords.

Microsculpture (Fig. 43B, C): Vermiform spiral threads not evident on early whorls; later whorls with a granular microsculpture on the spiral ribs and sparse scratch-like marks in the sculptural interstices.

Protoconch (Fig. 43A, C): White, a little exsert and slightly down-tilted; diameter ca 340 [micro]m; terminal lip very weakly convex; superficial sculpture well developed, arranged in irregular axial lines, spiral element weakly evident in some specimens.

Colour: White to pale greyish white, living specimens with dirty buff intritacalx deposit, particularly in sculptural interstices. Most material worn.

Dimensions: Largest specimen, length 4.2 mm, diameter 3.9 mm.

Operculum: Relatively tightly multispiral throughout.

Radula: Unknown.

External anatomy: Uniformly white and evidently chilodontid, but preservation of material inadequate to establish anatomical details.

Type material: The type lot at OXUM contains three specimens, one, the largest, is marked with an X in the aperture. It is here figured and designated lectotype (Fig. 42A). This is probably the originally figured specimen, but it is difficult to be certain since the original illustration was heavily retouched.

Additional material examined (all NMSA unless indicated otherwise): SOUTH AFRICA: Eastern Cape: off Mtamvuna River (31.1466[degrees]S 30.2666[degrees]E), living, -115 m, sponge and rocks, dredged NMDP, RV Meiring Naude, st'n A13, viii.1981 (E858); ditto (31.1483[degrees]S 30.2617[degrees]E), -111 m, sponge, dredged NMDP, RV Meiring Naude, st'n A14, 18.viii.1981 (E276); ditto (31.1500[degrees]S 30.2583[degrees]E), -110 m, some pebbles, dredged NMDP, RV Meiring Naude, st'n A9, 18.viii.1981 (E6993); off Port Grosvenor (31.4166[degrees]S 29.9667[degrees]E), -100-110 m, pebbles, some sand, dredged NMDP, RV Meiring Naude, st'n D6, 13.viii.1981 (E285); ditto (31.4166[degrees]S 29.9667[degrees]E), -95-100 m, coarse sand, few gorgonians, dredged NMDP, RV Meiring Naude, st'n D12, 16.viii.1981 (E6981); ditto (31.40[degrees]S 29.95[degrees]E), -80 m, calcareous coral nodules, lithothamnion sheets, dredged NMDP, RV Meiring Naude, st'n D20, 16.viii.1981 (S3174); ditto (31.3833[degrees]S 29.9333[degrees]E), -60 m, sand and broken shell, dredged NMDP, RV Meiring Naude, st'n D22, 16.viii.1981 (E6979); ditto (31.4166[degrees]S 29.9333[degrees]E), -82 m, worn coral nodules, dredged NMDP, RV Meiring Naude, st'n D18, 16.viii.1981 (E6980); ditto (31.4466[degrees]S 29.9333[degrees]E), -97-100 m, sandstone, pink gorgonians, dredged NMDP, RV Meiring Naude, st'n D14, viii.1981 (C974); offN'tafufu River (31.5783[degrees]S 29.6617[degrees]E), -50 m, mud and sand, dredged NMDP, RV Meiring Naude, st'n H6, 14.viii.1981 (E240); Mgazi River mouth (31.7283[degrees]S 29.5317[degrees]E), don. Mrs P. Palmer, viii.1980 (B3173); off Mbashe River (32.3567[degrees]S 29.0500[degrees]E), -465-500 m, coarse sand, dredged NMDP, RV Meiring Naude, st'n Q13, 6.vii.1985 (C9372); off Shixini Point (32.5267[degrees]S 28.8833[degrees]E), -500 m, muddy sand, coral rubble, dredged NMDP, RV Meiring Naude, st'n T17, 13.vii.1984 (V2786); off Qora River (32.5567[degrees]S 28.8000[degrees]E), -100 m, coarse sand, some sponge rubble, dredged NMDP, RV Meiring Naude, st'n U6,14.vi.1983 (E8266, S2657); off Qolora River (32.7848[degrees]S 28.5862[degrees]E), -340-350 m, coarse sand, broken shell, dredged NMDP, RV Meiring Naude, st'n Y11, 14.vii.1984 (E6997); East London, reef off Kwelera River (32.910[degrees]S 28.111[degrees]E), living, -20 m, dived B. Hayes, v.1992 (S6100); East London (33.0166[degrees]S 27.9166[degrees]E), ex Albany Mus. 1980 (B6626); Port Alfred (33.6[degrees]S 26.9[degrees]E), don. W.H. Turton, ex Albany Mus. 1980 (B7351); ditto, E.K. Jordan, ex Transvaal Mus. 1978 (B3416); Cannon Rocks (eastern end of Algoa Bay) (33.75[degrees]S 26.55[degrees]E), xii.1987 (E1539 and J. Marais coll'n 278); Port Elizabeth, Noordhoek (34.0405[degrees]S 25.6421[degrees]E), F. Graeve, ix.1985 (J. Marais coll'n 279); Port Elizabeth, Willows (34.0452[degrees]S 25.6070[degrees]E), living, under rocks ca low neap tide level, G. Carstens, 7.vi.1986 (D3493). Western Cape: Still Bay (34.3833[degrees]S 21.4500[degrees]E), purch. ex Mrs. C.M. Connolly, i.1974 (A3199) [record requires confirmation].

Distribution and habitat (Fig. 44): Eastern Cape, South Africa; from the border with KwaZulu-Natal, south and west to the Port Elizabeth area; empty shells from beach drift to -500 m; living intertidally (under rocks), or subtidally on firm substrata to -115 m. A single isolated record from 400 km further to the west at Still Bay (Western Cape) requires confirmation.

Remarks: This species closely resembles Vaceuchelus natalensis and was in fact treated as a synonym thereof by Barnard (1963). There are, nonetheless, clear and consistent differences evident in adult individuals which indicate that two distinct taxa are involved. The most obvious of these are the larger protoconch, closed umbilicus and presence of only three major cords on the base in V. gemmula. In addition, the spiral cords of V. natalensis remain strong at the aperture margin, producing strong notches in the outer lip even in the largest individuals. Juvenile stages can be difficult to separate since the umbilicus of V. gemmula sometimes only closes in the later stages of growth. Turton (1932) observed that the axial pliculae were more numerous in V. gemmula (about 30 on last adult whorl) than in V. natalensis (ca 20). I cannot confirm this observation and find considerable overlap between the taxa in terms of the number of axial pliculae, as well as considerable intraspecific variation. The three specimens in the OXUM type lot have 20, 22 and 24 pliculae on the last adult whorl, the latter figure being that of the lectotype. V. gemmula evidently attains a somewhat larger size than V. natalensis.

Little material of this species is available and most is in poor condition; only one live-collected adult specimen was to hand. The largest examples were obtained from beach-drift, but these are generally badly worn. Specimens from deeper water, off-shore habitats tend to be somewhat smaller, evincing an adult labrum at diameter ca 3.0 mm, and as in V. natalensis (below) they exhibit stronger nodules where the axial pliculae cross the spiral cords. The larger, less nodular form, which lives on near-shore reefs and washes ashore, is the typical form.

Vaceuchelus jayorum sp. n. Figs 45, 46, 49

Etymology: Named for Maurice and Danielle Jay of Reunion, in recognition of their contribution to our knowledge of the Mascarene malacofauna, and in gratitude for the hospitality they afforded the author.

Description:

Shell: Small, turbiniform (L/D=1.00-1.16); teleoconch of up to 3.5 whorls; sculpture strongly cancellate; first whorl initially sculptured only by axial pliculae, relatively widely spaced at first, but becoming more close-set toward end of first half whorl; 3 spiral cords develop during first whorl, one at mid-whorl, one between this and adapical suture and the third level with abapical suture; that at mid-whorl strongest and becoming peripheral cord of later whorls; cords become progressively stronger with growth, a fourth appearing below adapical suture during third whorl; axial pliculae more widely and regularly spaced from second whorl onward; pliculae cross cords producing angular nodules at intersections; in final quarter of last adult whorl an additional intermediary spiral cord arises between each of the primary cords (Fig. 45F); for the most part, intervals between cords noticeably wider than cords themselves; last adult whorl with 25-30 pliculae; pliculae narrower than cords; interstices obliquely quadrate. Base with 4 somewhat more close-set spiral cords, including that level with suture, a weaker fifth one sometimes evident, closely juxtaposed to the fourth and spiralling into umbilicus; umbilicus remaining patent at maturity, its width variable between individuals, often somewhat obscured by reflected upper part of columella lip. Peristome markedly oblique, almost tangential; aperture subcircular; columella concave, lacking dentition; outer lip notched at ends of spiral cords, somewhat thickened internally, but lacking both internal teeth and in-running ridges; interior of aperture nacreous, angled beneath external cords.

Microsculpture (Fig. 46B, C): Vermiform spiral threads not evident on apical whorls; microsculpture between axial pliculae crisply granular; this persisting over much of adult shell, but traces of scratch-like sculpture evident in interstices; in fresh specimens microsculpture generally obscured by relatively thick intritacalx layer and additional superficial encrustations.

Protoconch (Fig. 46A, C): White, not exsert, slightly down-tilted and more or less level with first teleoconch whorl; diameter 260-290 [micro]m; terminal lip straight but with evidence of a small beak-like projection near adapical suture; superficial sculpture well developed, relatively coarse and widely spaced, arranged in irregular axial lines, with no spiral component evident.

Colour: Shell more or less uniformly white to pale buff; with a dirty white, chalky intritacalx deposit.

Dimensions: Largest specimen, length 2.9 mm, diameter 2.5 mm.

Operculum: Like that of V. natalensis.

Radula and external anatomy: Unknown.

Holotype (Fig. 45A-C): REUNION: not further localised (M. Jay coll'n, MNHN 24809).

Paratypes: REUNION: Cap la Houssaye (21.01797[degrees]S 55.23709[degrees]E), -12 m, hand-dredged sand, J. Drivas, 1987 (NMSA K2755/T2959, 3 specimens); not further localised (M. Jay coll'n, MNHN 24810, 35 specimens; NMSA L8467/T2960, 4 specimens; NHMUK 20110385, 1 specimen). MADAGASCAR: Andramara (25.48000[degrees]S 44.97167[degrees]E), intertidal roche basaltique, dalles sableuses, Exped'n Atimo Vatae, st'n BM10, 2.vi.2010 (MNHN 24811, 2 specimens).

Other material examined: REUNION: not further localised (M. Jay coll'n, MNHN). RODRIGUES: Between Anse aux Anglais and Pointe Venus (19.6752[degrees]S 63.4313[degrees]E), beach-drift, D. Herbert, ix.1991 (NMSA K7825); Grand Baie, near stream (19.67175[degrees]S 63.45089[degrees]E), beach-drift, D. Herbert, ix.1991 (NMSA L549). MOZAMBIQUE: Inhambane area, off Ponta da Barra lighthouse, 'Stalin Reef' (23.68798[degrees]S 35.52566[degrees]e), -16 m, dived D. Slater, xi.2003 (D. Slater coll'n).

Distribution and habitat (Fig. 49): Endemic to the tropical south-western Indian Ocean, ranging from the Mascarene Islands, particularly Reunion, to southern Madagascar and central Mozambique. No accurate habitat data available, but probably an inhabitant of near-shore, carbonate substrata and perhaps lagoons.

Remarks: This material is confusingly similar to specimens of V. natalensis from off-shore habitats, in which the axial pliculae cross the spiral cords to produce a more angularly nodular sculpture. The principle discriminant character of the present material is the appearance of intermediary spiral cords above the periphery of the final quarter of the last adult whorl. Such intermediary cords are never evident in V. natalensis. In addition, the axial pliculae on the first teleoconch whorl are considerably more close-set in V. jayorum and the intritacalx deposit is more uniformly pale in colour, lacking the greyish axial banding common in V. natalensis.

There is also some resemblance to V. favosus (Melvill & Standen, 1896), a poorly known species from the Loyalty Islands. However, the figured syntype of that species (MMUM EE.3734; here re-illustrated and designated lectotype, Fig. 70E-G) also lacks intermediary spiral cords in the final quarter of the last adult whorl, and it has a wider umbilicus than any of the south-western Indian Ocean species of Vaceuchelus.

Vaceuchelus natalensis (Smith, 1906) Figs 4K, 6G, 47-49

Euchelus natalensis: Smith 1906: 55, pl. 8, fig. 5; Barnard 1963: 266 (in part). Type loc.: Durban, South Africa [H.C. Bumup].

Vaceuchelus natalensis: Poppe et al. 2006: 47.

Description:

Shell: Small, turbiniform; spire height rather variable (L/D=0.90-1.2); teleoconch of up to 3.5 whorls; sculpture strongly cancellate; first whorl initially sculptured only by relatively widely spaced axial pliculae (16-18), but 3 spiral cords develop soon thereafter, one forming shoulder, another level with abapical suture and the third between these, at whorl periphery; cords persist and become progressively stronger with growth; a fourth cord may develop on shoulder during last or penultimate whorl, but otherwise there are no intermediaries; intervals between cords noticeably wider than cords themselves; cords sometimes weakly and rather irregularly granular where crossed by axial pliculae (see notes below); last adult whorl with 22-30 pliculae; pliculae narrower than cords; interstices obliquely quadrate. Base with 4 somewhat more close-set spiral cords, including that level with suture, with a weaker fifth one spiralling into umbilicus; umbilicus narrowly patent, partly obscured by reflected columella lip. Peristome oblique; aperture subcircular; columella concave, lacking dentition; outer lip strongly notched at ends of spiral cords, even in the largest specimens; interior of aperture nacreous, lacking internal teeth or spiral ridges, but angled beneath external cords.

Microsculpture (Fig. 48B, C): Vermiform spiral threads not evident on apical whorls, but traces of microscopic granular sculpture present; scratch-like microsculpture weakly evident in sculptural interstices of adult shell, but microsculpture generally obscured by granular intritacalx deposit.

Protoconch (Fig. 48A, C): White, a little exsert and slightly down-tilted; diameter 280-300 [micro]m; lacking an apical beak; terminal lip more or less straight to weakly convex, and slightly flaring; superficial sculpture well developed, arranged in irregular axial lines, with no spiral element evident.

Colour: Shell whitish, living specimens with a dirty buff intritacalx deposit, usually with darker, ashy-grey axial bands, some iridescence in cord intervals; dead shells usually with only traces of intritacalx remaining, mostly in interstices.

Dimensions: Largest specimen, length 3.3 mm, diameter 3.4 mm.

Operculum (Fig. 4K): Relatively tightly multispiral throughout.

Radula (Fig. 48D, E): Formula [infinity]+2+1+2+[infinity]; ca 60 transverse rows of teeth; transition from lateral to marginal series relatively clear. Rachidian with large trigonal cusp and well-developed hood; cusp with very strong transverse ridge at its base; cutting edge coarsely dentate, central denticle largest, lanceolate, with approx. 4 smaller denticles on each side. Only 2 lateral teeth evident, their cusps spathulate with coarsely and deeply dentate margins. Marginals resembling those of Herpetopoma, the inner ones with cusp coarsely pectinate on outer margin; remaining marginals with smaller more finely pectinate cusps, but those at radula margin broader and flatter.

External anatomy (Fig. 6G): Head-foot translucent milky-white when alive, snout and neck with some greyish pigmentation. Cephalic lappets present but small and not extending across forehead; right postocular peduncle well developed, similar in size to eyestalk or perhaps larger; right subocular tentacle not evident; neck lobes similar, each with 5 or 6 tentacles of varying size; epipodium posterior to neck lobes with 4 or 5 tentacles of varying sizes on each side, with an epipodial sense organ faintly discernable at base of larger ones.

Type material: Lectotype (here designated, Fig. 47A-C) of Euchelus natalensis Smith, 1906, in NMSA (1208/T522), length 2.8 mm, diameter 2.9 mm; also three paralectotypes (NMSA W7531/T2642); three further paralectotypes in NHMUK (1906.6.23.18-20). All are fresh specimens, but none is obviously the one originally figured.

Additional material examined (all NMSA unless indicated otherwise): MOZAMBIQUE: Bazaruto Archipelago, Santa Carolina Is. (21.6124[degrees]S 35.3399[degrees]E), R. Kilburn, ix.1974 (K3929); ditto, south sandbank (21.6124[degrees]S 35.3399[degrees]E), R. Kilburn, 17.viii.1974 (K1991); Malongane, coral reef 5 km north Ponta do Ouro (26.7983[degrees]S 32.8906[degrees]E), -15-20 m, hand-dredged sand, D. Herbert, v.1994 (L1653). SOUTH AFRICA: KwaZulu-Natal: Kosi Bay, main reef 1-2 km south of estuary (26.9083[degrees]S 32.8861[degrees]E); -9-17 m, sorted from stone washings, D. Herbert, 12-20.vii.1987 (D9827); ditto, main reef, 1-4 km south of estuary mouth (26.9210[degrees]S 32.8861[degrees]E), living, -20 m, underwater pump, D. Herbert & R. Broker, 5.v.1990 (S2524); ditto, living, -15 m, stone surfaces, D. Herbert, 4.v.1990 (S2880); off Kosi mouth (26.9333[degrees]S 32.9117[degrees]E), -50 m, fine sand, shell rubble, Codium, dredged NMDP, RV Meiring Naude, st'n ZA2, 6.vi.1987 (E1468) between Bhanga Neck and Kosi Bay, reef off marker 13 north near pinnacles (26.93[degrees]S 32.90[degrees]E), -10-12 m, hand-dredged sand, D. Herbert, 12.v.1990 (S2482, S3106); ditto, -8 m, underwater pump, D. Herbert & K. Bloem, 6.v.1990 (S2769); off Dog Point (27.1083[degrees]S 32.8817[degrees]E), -70 m, sandstone conglomerate, dredged NMDP, RV Meiring Naude, st'n ZC3, 4.vi.1987 (E1736); off Lala Neck (27.2250[degrees]S 32.8250[degrees]E), -74 m, shells and sand, dredged NMDP, RV Sardinops, st'n ZDD3, 8.vi.1990 (S9768); Sodwana Bay, 2-Mile Reef (27.517[degrees]S 32.700[degrees]E), -10-15 m, sorted from stone washings, D. Herbert & R. Broker, ix.1987 (E740); ditto, -10-15 m, hand-dredged sand, D. Herbert, 30.xii.1990 (S4311); ditto, outer edge of reef, -15-17 m, sorted from stone-washings, D. Herbert, 18-26.x.1986 (D5298); Leadsman Shoal, outer portion (27.80[degrees]S 32.62[degrees]E), -24-26 m, sorted from stone washings, D. Herbert & NPB, 14.v.1988 (E2673); Leadsman Shoal, Raggie Reef, 1-2 km north of Leven Point (27.80[degrees]S 32.62[degrees]E), living, -8-12 m, mixed algal & coral reef, D. Herbert & NPB, 15.v.1988 (E6809); NE of Leven Point (27.9167[degrees]S 32.6467[degrees]E), -250 m, coarse sand, dredged NMDP, RV Meiring Naude, st'n ZL5, 9.vi.1988 (S1140); off Leven Point (27.9250[degrees]S 32.6083[degrees]E), -50-60 m, mud, dredged NMDP, RV Meiring Naude, st'n ZL1, 9.vi.1988 (E5873); Umdloti (29.6829[degrees]S 31.1127[degrees]E), intertidal, under rocks, ix.1974 (J. Marais coll'n 281); Durban (29.850[degrees]S 31.017[degrees]E), H.C. Burnup (A4564); Durban Bay (29.850[degrees]S 31.017[degrees]E), shallow dredgings, B.J. Young (E599); Umkomaas (30.2064[degrees]S 30.8023[degrees]E), living, H.C. Burnup (A4563); Widenham, intertidal rocks (30.216829[degrees]S 30.798644[degrees]E), low shore spring tide, under large rocks with spaces below, together with arcid and carditid bivalves, leg. D. Herbert & L. Davis, 23.ix.2010 (W7462); Aliwal Shoal (30.2833[degrees]S 30.8333[degrees]E), D. Herbert 6 R. Emanuel, 27.xi.1988 (E6189); ditto, -10 m, sand & reef debris, hand-dredged, D. Herbert, 4.iv.1992 (S8222); ditto, -10-20 m, hand-dredged sand, D. Herbert, 30.vi.1991 (S8021); ditto, -14 m, underwater pump, D. Herbert, 2.vi.1991 (S8673); ditto, -16 m, hand-dredged sand, D. Herbert, 26.v.1990 (S5993); ditto, -27 m, in silt from between rocks, G. Smith, don. J. Marais, iii.1988 (E1675, J. Marais coll'n 280); ditto, Cracker Reef, ca -23 m, D. Herbert, 30.iv.1989 (E7141); Scottburgh (30.283[degrees]S 30.833[degrees]E), C.W. Alexander, ex W. Falcon coll'n (A4565); Landers Reef off Park Rynie (30.333[degrees]S 30.817[degrees]E), -29-30 m, sorted from stone washings, D. Herbert, 2.v.1988 (E2251); off Umzinto (30.36[degrees]S 30.85[degrees]E), living, -84 m, dredged NMDP, RV Meiring Naude, st'n X2, 15.viii.1982 (D5428). Eastern Cape: Mbotyi (31.45[degrees]S 29.73[degrees]E), beach drift, R. Kilburn & D. Herbert, v-vi.1985 (C8468); Lwandile/Mdumbi (31.883[degrees]S 29.267[degrees]E), R. Kilburn & R. Fregona, vii.1981 (C205); Xora River mouth (32.1600[degrees]S 28.9974[degrees]E), R. Kilburn (7059); off Nthlonyane River (32.2133[degrees]S 28.9817[degrees]E), -51 m, sandy mud with astrorhizid foraminiferans, dredged NMDP, RV Meiring Naude, st'n P7, 19.vi.1982 (E164); Pondoland coast, Mrs A. Filmer, H. Becker coll'n, ex Transvaal Mus. 1978 (B1104).

Distribution and habitat (Fig. 49): Southern Mozambique (Bazaruto Archipelago) to just north of the Mbashe River, Eastern Cape, South Africa; from the low intertidal zone of rocky shores to -84 m; in intertidal habitats specimens may be found living at LST under large rocks that are rarely moved by the waves and which have a space beneath them allowing water flow, usually together with arcid and carditid bivalves. I believe Turton's record of the species from Port Alfred, Eastern Cape (Turton 1932) was almost certainly based on material of V. gemmula, which Bartsch had earlier mistakenly identified as V. natalensis.

Remarks: There is noticeable intraspecific variation in the extent to which the axial pliculae interact with the spiral cords. In intertidal material the interaction is minimal and the spiral cords are smooth or at most irregularly undulant. This is the typical condition (Fig. 47A-G). Generally, in specimens from off-shore reefs, however, the axial pliculae are more close-set and they cross the spiral cords, rendering the latter distinctly nodular (Fig. 47H, I). Such specimens closely resemble V. jayorum from Reunion, but they do not develop intermediary spiral cords on the last adult whorl. The distinguishing features of V. gemmula have been detailed above.

V. cavernosus (Sowerby, 1905) from Sri Lanka (Fig. 70A, B) and V. clathratus (A. Adams, 1853) from the Philippines (Fig. 70C, D) likewise lack apertural dentition, but are both considerably larger, whereas V. semilugubris (below) although equally small, generally has blackish maculations and develops denticles inside the outer lip when mature.
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Title Annotation:p. 420-461
Author:Herbert, D.G.
Publication:African Invertebrates
Article Type:Report
Geographic Code:0INDI
Date:Dec 1, 2012
Words:16650
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