131 
FISSURELLA, Bruguieres. 
Gen, Char, j Shell obliquely conical, in no part 
spiral, with an oblong aperture in the vertex, 
and an oval base. 
This Genus of sheik, so nearly resembling Patella, is 
well distinguished from it by the perforated vertex 
through which the branchiae 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. 
