262 



POPULAR CONCHOLOGY. 



cular, tumid, its mantle freely open in front, with plain or 

 less frequently fringed edges, conspicuously fimbriated in 

 the neighbourhood of the very short, slightly separated 

 siphons, the branchial one of which, is always fringed at 

 the orifice ; foot very large, cylindrical, geniculated ; 

 branchial leaflets unequal, labial palpi rather long, and 

 triangular.* — 133 species f; also fossil. 



Some of the species are very beautiful, and others very 

 singular in form ; amongst the latter is the species Car- 

 dium cardissa, in which the valves are flattened, but in a 

 contrary manner to the generality of flat Bivalves. This 

 genus is found almost everywhere lying buried in the sand 

 near the sea-shore, but by means of their long elbow- 

 shaped foot, the animals have the power of leaping to a 

 considerable distance. Cardium edule, the common spe- 

 cies, is frequently used as an article of food, and in 

 times of scarcity is most valuable. The most striking 

 in form and colour, are found in the Indian Ocean, and 

 the African Seas. There are many beautiful fossil species 

 of this genus, of which more than thirty are found in 

 British strata. 



Philippi includes as sub-genera : — Cardissa Meg. and 

 Muhlf. ; Adacna, Monodacna, and Didacna of Eichwald ; 

 and Serripes of Beck. 



Protocardia. Beyrich. — Shell equivalve, somewhat 

 equilateral, globose, truncated behind, and the edges of 

 the valves untoothed ; one or two cone-shaped hinge 

 teeth, and on each side a lateral tooth ; the pallial impres- 

 sion has a sinus behind. The upper surface is entirely 

 smooth, or transversely furrowed, the posterior side only 

 having radiated stripes. — Fossil. 



* Forbes' s British Moll. 



| Reeve's Iconiea.- 



