Chilonopsis subplicatus (G.B. Sowerby I, 1844)

Chilonopsis subplicatus (G.B. Sowerby I, 1844)

Figs 4g View Fig , 7g –h View Fig , 10c–d View Fig

Cochlicopa subplicata G.B. Sowerby I, 1844: 156 .

Cochlicopa terebellum G.B. Sowerby I, 1844: 156 .

Bulimus subplicatus – Forbes 1852: 199. — Melliss 1875: 122.

Bulimus terebellum – Forbes 1852: 199. — Melliss 1875: 122.

Achatina subplicata – Melliss 1875: 123.

Subulina subplicata – Wollaston 1878: 552.

Subulina terebellum – Wollaston 1878: 552.

Bulimus (Peroneus?) subplicatus – Smith 1892: 266.

Pachyotus subplicatus – Dall 1896: 419.

Chilonopsis subplicatus – Pilsbry 1904: 178. — Crowley & Pain 1977: 558.

Chilonopsis subplicatus var. terebellum – Pilsbry 1904: 179.

Chilonopsis (Chilonopsis) subplicatus – Germain 1931: 170.

Diagnosis

The only fusiform Chilonopsis ; spiral striae on the base coarser than in other species; columellar ridge distinctively concave.

Type material

Type of Cochlicopa subplicata

Not located, collected by Charles Darwin, Flagstaff hill ( Darwin 1836).

Type of Cochlicopa terebellum

Not located, collected by Charles Darwin, Flagstaff hill ( Darwin 1836); said to be in the collection of Charles Lyell ( Forbes 1852), figured by Forbes (1852) ( Fig. 10c View Fig ). The Darwin specimens have not been located in the Lyell collections of the Oxford University Museum or the NHMUK (J. Ablett, E. Howlett, C. Sendino pers. com.).

Other material examined

SAINT HELENA • 2 shells; ANSP MAL 69938 About ANSP • 1 shell; MCZ 381472 About MCZ • 18 shells; Castle Rock Plain (GB 882 SH); 1995; P. and M. Ashmole leg.; MSH (1 used in SEM) • 1 shell; Flagstaff Hill ; E.W. Alexander leg.; NHMUK 1857.10 About NHMUK .16.34 • 5 shells; W.H. Turton leg.; NHMUK 1892.2.24.176- 181 • 1 shell; A.J. Piele collection; NHMUK 2242 About NHMUK • 3 shells; Sandy Bay PG1 valley toward Potato Gut, surface finds; Aug.–Sep. 2022; “AtlantAves” leg.; NHMUK 20240182 About NHMUK • 3 shells; burrow 100 m NE of Olsen site A, Sandy Bay; Aug.–Sep. 2022; “AtlantAves” leg.; NHMUK 20240183 About NHMUK • 1 shell; above Potato Bay ; 1981; D.G. Llewellyn leg.; 1981; NHMUK • 1 shell; W.H. Turton leg.; Tomlin collection; NMW • 3 shells; Tomlin collection; UMMZ 141297 View Materials • 6 shells; USNM 126270 About USNM .

Description

A relatively small species (height 17.0– 25.4 mm; Table 1 View Table 1 ). Elongately fusiform. Apex flat. 5.5–7 very slightly convex whorls. Protoconch of 1.5 whorls ornamented with 5 very fine spiral striae. Teleoconch with fine spiral striae on first three whorls, interrupted by radial ridges; coarse spiral ridges on lower half of each whorl, visible just above suture and on body whorl. Strong radial ridges on all whorls, sinuous at the sutures and where they cross the spiral striae. Semi-regular radial ridges forming raised bosses at suture on 3 rd –6 th whorls; body whorl of large adults smooth. Body whorl slightly angled at margin. Aperture distinctly slanting, ovate, becoming broadened and with a flaring lip in fully mature individuals (“C. terebellum ”). The outer lip is simple, margins joined by a thin parietal callus. Columella dilated, twisted in middle, forming a concavity. Umbilicus very narrow. Grey-brown to reddish with white mottling and diagonal streaks markings, sutural bosses white. Apex usually reddish.

Distribution

Widespread ( Fig. 11 View Fig ). Published material is restricted to the north of the island; Flagstaff Hill ( Darwin 1836), Sugarloaf Ridge ( Smith 1892); Side Path (between Jamestown and Longwood, side of the hill overlooking the Briars – Wollaston 1878). New material collected from the south of the island: Sandy Bay (new). Chilonopsis terebellum only recorded from Flagstaff Hill ( Darwin 1836) and Sugarloaf Ridge (NHMUK 1892.2.24.176–181). Considered extinct in 1892 ( Smith 1892), although some of Turton’s specimens from 1884–86 were fresh.

Remarks

Bulimus terebellum was synonymised with C. subplicatus by Smith (1892), a lead followed by Germain (1931), whereas Pilsbry (1904: 179) retained var. terebellum Sowerby as a larger, smoother form with a more expanded aperture; these differences can mostly be attributed to different stage of maturity and some samples (e.g., MSH and NHMUK 1892.2.24.176–181) include both forms from the same locality.