334 TROCHID.E. 



rounded base, rather thin, semitransparent and glossy : sculp- 

 ture, four or five concentric, prominent, and sharp ridges on 

 the upper part of the last whorl ; on the base are three ridges 

 immediately below the periphery, and three or four more (se- 

 parate from the last) on the umbilical area ; the penultimate 

 and preceding whorls have similar ridges, which gradually de- 

 crease in number upwards ; those on the three or four smaller 

 whorls, and occasionally some of the other ridges, are granu- 

 lated or beaded ; the apex is rounded, and pitted like the top 

 of a thimble ; the furrow or space between each ridge on the 

 larger whorls is flat, three or four times as broad as the ridge, 

 and indistinctly lineated in a spiral or concentric direction ; 

 the whole surface is covered with very minute close-set and 

 oblique longitudinal strise : colour opaline, with the ridges of 

 a pale golden or light yellowish-brown hue : spire gradually 

 raised, and terminating in a sharp point : ivliorls 7-8, some- 

 what convex ; the last is proportionally much larger than the 

 next, and the same as to each of the rest in succession : 

 suture slight, but well defined in consequence of the convexity 

 of the whorls : mouth roundish, angulated above, and spread 

 out below : outer Up thin, indented or scalloped by the ridges : 

 inner lip nacreous and reflected on the pillar, which is thick 

 and curved, with an oblique but slight excavation behind it : 

 inside iridescent : operculum very thin, slightly concave, with 

 a small central pit, having from 15 to 18 turns, and micro- 

 scopically striated in the line of growth. L. 0*5. B. 04. 



Yar. pura. Altogether pearl-white. 



Habitat : Stony or iC hard " ground on the fishing- 

 banks of Shetland, in 40-90 f. ; not uncommon in some 

 places. Also from 40 to 80 f. on both sides of the 

 Orkneys, and in 60 f. off Troup Head, Aberdeenshire 

 (Thomas) ; among the refuse of a long-line fishing-boat 

 at Peterhead (Peach) . Two other British localities have 

 been published ; but the first has since been admitted 

 to be erroneous, and the second is very questionable. 

 These are Moray Firth (Gordon), and Lamlash Bay in 

 the Clyde district (Eyton) . The variety is Zetlandic, 

 and occurs with specimens of the usual colour. Bed 

 and Coralline Crag (S. Wood) ; Lillo, on the banks of 



