RISSOA. 127 



R. PKOxiMA, Alder. 

 Resembling vitrea, but spirally striated. 



Plate LXXV. fig. 7, 8. 



Rissoa slrialida (not of authors), Jeffreys, Ann. Nat. Hist. vol. xx. p. IfJ. 

 „ proaima. Alder MSS. ; Thompson, Ann. Nat. Hist. vol. xx. p. 174 (no 



description). 

 „ virginea. Brown, Illust. Conch. G. B. p. 13, pi. 9, f. 82 ? 



Although bearing so strong a likeness to vitrea^ that 

 instead of describing it at large, we need only particular- 

 ize its points of dissimilarity, we cannot hesitate to assent 

 to the perfect specific distinctness of this graceful little 

 shell. The regular, though vei-y minute raised lines, that 

 densely encircle the entire surface of its larger whorls, 

 enable us readily to distinguish a well preserved specimen 

 from its closely allied congener; and even where an un- 

 natural smoothness results from long attrition upon the 

 shore, the practised eye of a conchologist will detect 

 each individual by its more compact style of gyration. 

 For the whorls, not being loosely coiled, as in the pre- 

 ceding species, are rounder and less produced, and the 

 suture, which is profound or even subcanaliculated, is less 

 oblique. The apex of the shell is rather more depressed, 

 and the mouth, owing to the penult not being quite so 

 disproportionately large, is slightly longer than the whorl 

 above it. Its usual size is a little less than that of the 

 last species. 



This rare species has been found in Cork Harbour, 

 Bantry Bay, Portmarnock, and Dublin Bay (Jeffreys). 

 It is the vitrea of Mr. Thompson's Report on the Fauna 

 of Ireland ; he observes it has been obtained sparingly 

 on each side of the Irish coast. 



