131 



FISSURELLA, Bruguieres. 



Gen. Char. Shell obliquely conical, in no part 

 spiral, with an oblong aperture in the vertex, 

 and an oval base. 



This Genus of shells, so nearly resembling Patella, is 

 well distinguished from it by the perforated vertex 

 through which the branchias are supplied with a current 

 of water. Many of the species have diverging rays upon 

 their surface, and crenated edges ; others are smooth : 

 some are without colour ; others variously ornamented 

 with red, brown, &c. The vertex is inclined towards 

 the head of the animal, and has within it a kind of 

 fringed ring, formed by the thickening of the edge of the 

 perforation. As this part varies in form and colour in the 

 different species, it is often of service in forming speci- 

 fic characters. The animal differs from that of Patella, 

 in having the branchiae situated in an appropriate cavity, 

 and not around the mantle. 



