226 JOURNAL OF CONCHOLOGY, VOL. 9, NO. 8, OCTOBER, 1899. 



solidity and contracted mouth are constant characters, but it must be 

 pronounced variable in shape and convexity of whorls. Some are 

 quite as cylindrical as O. clavula, but the compressed whorls and 

 conspicuous umbilicus of the latter will always distinguish them. 

 Others closely approximate to forms of O. risso'ides, but in these cases 

 the smaller mouth of O. lukisi will separate them. A prevalent form 

 from Torbay (of which the young are globose) is short and stumpy; 

 and a dwarf form occurs at the Isle of Man and in South Devon. 

 The finest come from Jersey, Margate, and Shetland, and attain a line 

 and a half. It is more plentiful at Guernsey than elsewhere, where it 

 was first discovered. Plenty of specimens are without the umbilicus, 

 and that and the tooth are never so prominent as in Jeffreys' figure, 

 which is otherwise a good one. Sowerby's figure (pi. 17, fig. 18) is 

 not this species, but O. risso'ides. 



O. albella Lov. — Jersey to Shetland. 



Var. subcylindrica Marsh 1 . — Jersey and Guernsey ; Scilly 

 Islands; Bantry Bay. 



This species is most abundant in the Channel and Scilly Islands, 

 but rather scarce elsewhere. It is not a variable shell, although in 

 outline it ranges from cylindrical to oval. It is of a dull glassy white, 

 the liver-spot showing through in living specimens, and the peculiar 

 generic nucleus always shows up well. It has a very small umbilicus 

 or chink placed exactly opposite a very small tooth ; neither tooth nor 

 umbilicus, however, is always visible. A dwarf form lives under stones 

 at Guernsey quite high up, with Littorince. A telescoped monstrosity 

 comes from Scilly, and a decollated one from the same district and 

 from Falmouth. 



Jeffreys' figure is perfect; Forbes and Hanley's (as O. risso'ides var. 

 albella) is not near the mark, and why coloured brown it is hard to 

 say; Sowerby's is nothing like. 



O. rissoides Hani. — Between tide-marks and dredged dead at all 

 depths. This shell is extremely variable in size, comparative con- 

 vexity of whorls, and shape; some are cylindrical, others oblong, 

 conical, oval, and globose, but in all its many forms differing from the 

 preceding and following species in its texture, deeper suture, and 

 rounded aperture. The turreted whorls and deeper suture are its 

 most constant characters. The tooth and umbilical chink, in the type 

 and all the varieties, are of too variable a character to be relied upon, 

 specimens of the same proportions and from the same localities show- 

 ing one or both quite conspicuously, while in others they are obscure 

 or altogether wanting. Jeffreys says that " in specimens which have a 

 short spire there is a more or less developed chink or indentation," 



1 /. Conch., vol. 7, pp. 252-3, 1893. 



