Clavus humilis (E. A. Smith, 1879)

Kilburn, Richard N., Fedosov, Alexander & Kantor, Yuri, 2014, The shallow-water New Caledonia Drilliidae of genus Clavus Montfort, 1810 (Mollusca: Gastropoda: Conoidea), Zootaxa 3818 (1), pp. 1-69 : 32-34

Clavus humilis (E. A. Smith, 1879) .

( Figs. 15 A–E)

Drillia humilis E. A. Smith 1879: 193 , pl. 19, fig. 20.

Other references.

Drillia humilis ; Shuto 1975: 165, pl. 6, fig. 5 (apex of holotype).

Tylotiella humilis ; Higo et al. 1999: 297; Higo et al. 2001: 99 (textfig. of holotype).

Clavus (Tylotiella) mighelsi sensu Kay 1979: 346 , fig. 115J (vide infra).

? Tylotiella humilis ; Habe 1958: pl. 3, fig. 6 (radula).

? Clavus (Tylotiella) humilis; Kuroda et al. 1971: 205, pl. 58, fig. 5; Hasegawa et al. 2000: 619, pl. 308, fig. 5 (identification requires confirmation).

Type data. Holotype NHMUK 1878.11.7.14. Type locality: Ojica Bay, Goto Islands, Japan, 33º12.5'N, 129º05'E, 10 fath. [18 m].

New caledonian material examined (total 16 lots, 86 spms):

New Caledonia, EXPÉDITION MONTROUZIER, Touho Stns. 1245 (9 spms), 1250 (2 spms), 1255 (4 spms), 1259 (15 spms), 1260 (13 spms), 1261 (9 spms), 1266 (3 spms);

LAGON, Stns. 614 (1 spm), 656 (2 spms), 712 (1 spm). Coral Sea, CHALCAL, Stn. DC9 (1 spm).

Distribution. Hawaii to New Caledonia, Coral Sea and Japan, intertidal to ca 50 m, in our material confirmed live to 35 m.

Description. Shell small (to ca 11 mm), biconic-claviform (breadth/length 0.38–0.44), spire initially somewhat coeloconoid, later cyrtoconoid (eg shell slightly pupoid), apex papilliform, aperture relatively large (aperture/total length 0.36–0.44), somewhat linear, slightly constricted below; lip weakly alate below anal sinus; base moderately broad, truncate, slightly oblique, not indented, without fasciole. Outer lip weakly convex in side view, anal sinus not deep, openly U-shaped, parietal pad rounded, not constricting anal sinus; stromboid notch present.

First teleoconch whorl weakly convex, subsequent whorls progressively more convex anteriorly, penultimate whorl most strongly so, subsutural region weakly concave, adpressed to previous whorl, suture shallow, somewhat irregular. Sculptured by low axial ribs, suture-to-suture on first teleoconch whorl, a slight subsutural concavity developing on second whorl, then ribs weakening below suture until by last whorl they have become weak to obsolete on posterior third to half whorl; opisthocline, procurved below suture, on base evanescing at parietal level; in t/s angularly rounded, subequal to intervals; 10–12 per whorl. Varix rounded, moderately low, a short distance behind lip. Rostrum with 5–6 close-set, rather flattened spiral ridges. Microsculpture of relatively coarse axial threads and finer spiral striae, finest below suture.

Colour medium reddish-brown with a white band around periphery of last whorl, subsutural region paler brown, sometimes with brown blotches, a thin brown spiral line, usually interrupted by ribs, above periphery; last whorl with a row of inconspicuous pale dots on bases of ribs at level of parietal callus; base sometimes paler brown, so that more conspicuously spirally zonate; aperture and inner lip (including parietal nodule) brown.

Protoconch strongly eroded in available material, somewhat globular, of ca 1.6 whorls, smooth except for traces of axial threads behind protoconch-teleoconch termination, white; diameter ca 600 µm.

Measurements. Largest and smallest New Caledonian examples: 10.1 x 3.8 mm and 7.8 x 3.4 mm, respectively.

Remarks. Although variable, most New Caledonian shells agree well with the holotype of Drillia humilis , but also with Hawaiian specimens that are clearly referable to the species figured and described by Kay (1979: fig. 115J) as her Clavus mighelsi . This was proposed as a substitute name for Pleurotoma acuminata Mighels, 1845 , non J. Sowerby, 1816. However, the latter name evidently has not been correctly applied. Not only does Mighels’ reference to his type as “wax-coloured” conflict, but photographs of the lectotype designated by Johnson (1949: 221, pl. 17, fig. 18), kindly supplied by Adam Baldinger, bear no resemblance to mighelsi auct., and the species concerned is not even a Clavus but probably belongs to the mangeliine genus Pyrgocithara Woodring, 1928 .

Difficulty in identifying Mighels’ briefly described and unfigured species is historical. The figure given by Martens & Langkavel (1871: 1, fig. 1) for Drillia acuminata “Pse ” does not resemble the present species as it shows a narrow shell with close axial ribs, uninterrupted by a depression. The figure given by G. & H. Nevill (1875: 84, pl. 8, fig. 14) of an Andaman Island specimen (which was pronounced by them as “in no respect” differing from typical Hawaiian examples), does not agree with the latter either; possibly they were misled by a misidentified shell in the Cuming collection (NHMUK) labelled “Sandwich Is”.

Of New Caledonian taxa the only species similar to Clavus humilis is Clavus protentus , which differs in its prominent peripheral nodules, which do not extend onto the base as axial ribs.

Figures

FIGURE 15. Clavus humilis (E. A. Smith, 1879). A. Drillia humilis, holotype NHMUK 1878.11. 7.14, Ojica Bay, Goto, Japan, 18 m; 9.5 x 3.4 mm; B, C. New Caledonia, LAGON, Stn. 656, Canala Sector, SL 12.8 mm; D, E. New Caledonia, EXPEDITION MONTROUZIER, Touho Stn. 1261, SL 9.7 mm.