38 LITTORINIDiE. 



colour, and occupies from, at least, four-sevenths to fully 

 one half the entire length of the shell. The outer lip 

 is simple, acute, and peculiarly projecting and rounded, 

 especially posteriorly, where its junction with the body is 

 nearly subrectangular. The pillar (in the adult) is almost 

 equally broad throughout, somewhat concave, and not 

 at all produced ; the length of the mouth is but little 

 diminished by its confluence with the outer lip. 



We have figured an oblique and patulous variety, of 

 which we possess two forms, one resembling the type in 

 its possession of riblets, the other actually smooth upon 

 the body-whorl towards the outer lip. The colouring 

 of the latter, which is evidently the labiata of Brown, 

 is pale yellow, adorned with encircling interrupted streaks 

 of reddish brown. 



The characters of its aperture distinguish it from the 

 aberrant ridged variety of rudis so specially indicated in 

 our description of that species; for, in that shell, the 

 anterior extremity of the mouth is filled up by the broad 

 confluence of the suddenly expanding pillar with the outer 

 lip. The acuteness of its apex, its comparative solidity, 

 and the more shelving roundness of its penult volution, aid 

 us in separating it from its closely allied congener. 



The majority of individuals do not exceed the third 

 of an inch in length or breadth, but one of our specimens 

 of the wrinkled or typical variety, measures nearly half 

 an inch in either direction. This specimen was obtained 

 from the vast pile of rocks near the caves in Freshwater 

 Bay, Isle of Wight (S. H.), where the species is met 

 with in abundance, along with petreea and rudis, each 

 preserving, however, its peculiar situation upon the same 

 stone. 



The ridged forms arc procured both on the north and 



