Chilonopsis subplicatus MSH

Chilonopsis subplicatus (G.B. Sowerby I, 1844) Figs 4g, 7g –h, 10c–d 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). 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 • 1 shell; MCZ 381472 • 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 1857.10.16.34 • 5 shells; W.H. Turton leg.; NHMUK 1892.2.24.176- 181 • 1 shell; A.J. Piele collection; NHMUK 2242 • 3 shells; Sandy Bay PG1 valley toward Potato Gut, surface finds; Aug.–Sep. 2022; “AtlantAves” leg.; NHMUK 20240182 • 3 shells; burrow 100 m NE of Olsen site A, Sandy Bay; Aug.–Sep. 2022; “AtlantAves” leg.; NHMUK 20240183 • 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 • 6 shells; USNM 126270. Description A relatively small species (height 17.0– 25.4 mm; 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). 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.