48 LITTORINIDiE. 



The breadth of a full-sized individual of the former 

 variety was three quarters of an inch, and its length only 

 half; an example of the latter variety measured seven and 

 a half lines broad, and seven lines long. 



The animal is usually of a bright yellovi^ colour, but 

 occasionally, as in a variety we have taken in the Isle of 

 Man, is tinged with dusky, and has the tentacula and 

 muzzle nearly jet black. The former organs are slen- 

 derer than in its congeners, and the eyes placed rather 

 farther back. The mantle in the former variety is edged 

 with orange, in the latter with a black line. The opercu- 

 lum is tinged with rich brown. 



This species is abundant all round the British and Irish 

 coasts, living on Fuel, between tide-mark, but more espe- 

 cially inhabiting the third subregion of the Littoral zone, 

 that of Fucus serratus, where it is found in company with 

 Trochus cinerarius. It ranges along the shores of tlie 

 Northern and Celtic provinces on the European side of the 

 Atlantic. 



species : — " Shell strong, subconic, smootli ; spire very short, being about one- 

 fourth of the length of the body, consisting of four well-rounded volutions ending 

 in an obtuse apex ; body large, tumid, crossed by some obscure lines of growth, 

 its upper margin provided with a narrow spiral groove, which continues throughout 

 the volutions; aperture subrotund, d;irk purplish brown within, pale fawn colour 

 within the margin of the inner lip, which is thin, and not continuous; pillar lip 

 glossy, white or pale reddish purple, broadly reflected on the columella, with a 

 very slight subumbilicus behind. Length nearly five-eighths ; breadth upwards 

 of three-eighths. 



" We discovered this species adhering to rocks below high-water mark, near 

 Downpatrick, Ireland, where it is very plentiful." 



