168 PYRAMIDELLID.i:. 



Shell shorter and more cylindrical than 0. lactea, being of 

 nearly equal breadth throughout, instead of pyramidal and 

 becoming gradually broader towards the base ; it is also more 

 solid ; the ribs are always curved, but not set obliquely, and they 

 do not terminate quite so abruptly below the periphery ; the 

 whorls, although equal in number, are more rounded and com- 

 pact, those near the apex rapidly increasing, so as to give that 

 part a quasi-truncated appearance ; the base is usually more 

 contracted ; and the tooth (or rather the fold or plait) is fre- 

 quently visible, just below the angle formed by the pillar with 

 the upper slope of the base, and by breaking the shell this may 

 be traced winding round the pillar. L. 0-275. B. 0-075. 



Habitat : With the last species, but hitherto noticed 

 as found only in the undermentioned places : — St. 

 Catherine's Bay, Jersey (Norman) ; Guernsey, Lul- 

 worth, and Torbay (J. Gr. J.) ; Littleham Cove, Ex- 

 mouth (Clark) ; Burrow Island (Barlee) ; Falmouth 

 (Hockin); Barrycane, North Devon (Miss Jeffreys); and 

 Ilfracombe (Alder). Loire-Inferieure, among Zostera 

 marina (Cailliaud) ; Gibraltar (M^Andrew) ; Gulf of 

 Lyons (Martin); Cannes (Mace); Spezzia (Marquis J. 

 Doria and J. G. J.) ; Tarento (Philippi) ; and Algiers 

 (VVeinkauff). 



According to Mr. Bretherton, this species creeps 

 quickly over the sand at the bottom and along the sides 

 in an aquarium, but very frequently falls off the slippery 

 surface of the glass ; the shell is dragged rather than 

 borne. In comparing it with what Mr. Clark appro- 

 priately calls its stately congener (0. lactea), size is not 

 the only distinctive mark. A specimen of the present 

 species as large as an ordinary one of the other, pre- 

 sents all the peculiar characters w^hich I have pointed 

 out. In at least 100 specimens of each examined by 

 me, not one occurred of an intermediate kind. 



Chemnitzia pusilla of the late Professor Adams (1850), 

 from Jamaica, is a different species. 



