36 LITTORINIDif:. 



the ribs are encircled by a white line ; the tip in worn speci- 

 mens is frequently purplish : spire abruptly tapering to a fine 

 point : u'Jiorls 8, convex, the lower two being equal in breadth, 

 and the penultimate sometimes even slightly broader than the 

 last ; the upper whorls rapidly diminish in size ; and those 

 forming the point of the spire are disproportionately small 

 and flattened : suture rather deep : mouth roundish- oval, con- 

 tracted and incurved above, slightly expanding at the sides 

 and below: outer lip thin beyond the large rib or callus 

 which strengthens the mouth : inner lip considerably reflected 

 on the pillar and towards the base : operculum pale-horncolour, 

 of three rapidly increasing volutions, and finely striated. L. 0*2. 

 B. 0-075. 



Habitat : Codium foment osum and other small sea- 

 weeds at low-water^ in the Channel Isles and on the 

 coasts of Dorset and Devon ; also at Ryde (Hanley) ; 

 Worthing (Eich) ; Manorbeer in Pembrokeshire, and 

 Cork (J. G. J.) ; Scarborough (Bean) ; Lamlash (Lands- 

 borough). Probably the last locality^ and certainly 

 Connemara (given by Forbes and Hanley on the late 

 ]Mr. Thompson's authority), appertains to R. violacea, 

 instead of to the present species. R. costulata inhabits 

 the northern and western coasts of France (Mace and 

 others), Gijon, Corunna, and Vigo (M' Andrew), and 

 both sides of the Mediterranean. Specimens from that 

 sea are smaller and more slender than those from the 

 North Atlantic. There are two sizes everywhere, appa- 

 rently representing a difference of sex. 



I found a living specimen at Lulworth which had the 

 lower half broken off and a new mouth formed among; 

 the ruins. 



It is not R. costulata of Eisso (which is R. costata, 

 Desmarets, and i?. variabilis, y. Mulilfeld) , nor R. costu- 

 lata of Searles Wood, from the Coralline Crag. Leach 

 called the present species Persephona Goodallana and 

 P. rufilabris, judging from his description of the former, 



