270 PYRAMIDELLIDiE. 



tinct umbilicus. The columellar fold is small, sluii|), 

 horizontal, and distinct : it lies almost in the middle oi the 

 inner lip. The usual length is only two lines, with a 

 breadth of two-thirds of a line. 



" The ground-colour of the animal is white ; the man- 

 tle simple ; the foot short, flake-white, in front deeply 

 emarginate, so much so, as at times to present the ap- 

 pearance of a second pair of short tentacula, it rounds 

 gradually to a blunt point, and carries a suboval ellip- 

 tically striated corneous light horn-coloured operculum on 

 a simple upper lobe. The head is a moderately elongated 

 muzzle, marked with minute lead-coloured blotches. The 

 tentacula are short, broad, awl-shaped, but not pointed, 

 setose, eyes close together, immersed in the skin between 

 their internal angles. The tentacula have an intensely 

 white longitudinal line running from base to point in each. 

 Branchial plume ? This species is rare in the coralline 

 zone. The animal is lively, not at all shy, and makes 

 rapid progression." — Clark MSS. 



A rather larger variety is found, of a dull white, which 

 has more rounded volutions, and its periphery devoid of all 

 angularity. This last character seems to connect the 

 species with the umbilicata of Alder (Trans. Tyneside Nat. 

 Club, 1850), the periphery of which is well rounded or even 

 ventricose. The only individual we have ever seen of it 

 (kindly forwarded to us by the author) only diifers from 

 acuta proper in its snow-white hue, and more broadly 

 conic shape ; hence we provisionally regard it as a northern 

 variety of this species. It came from Tynemouth ; its 

 axial perforation is very conspicuous. 



It ai)pears to be a somewhat local species, but is toler- 

 ably abundant at certain spots. It was dredged alive, in 

 company with Chemnitzia fenestrata, in rather shallow 



