274 



POPULAR CONCHOLOGY. 



to the pallial impression; limule almost always distinct. 

 Animal the shape of the shell, and never exceeding it ; its 

 mantle freely open with plain (always ?) margins, slightly 

 united posteriorly at two points, so as to form two siphonal 

 orifices, both with simple edges ; foot linguiform, strong 

 but not large; labial tentacles large, lanceolate; leaflets of 

 each pair of branchiae equal, or nearly so.* — Many 

 species ; also fossil. 



Six of the species are found on the British shores ; the 

 one most commonly known is A. danmoniensis. One is 

 found is Sicily, others in America ; they are generally on 

 sandy mud at variable depths. 



Pronoe. Agassiz. — Shell separated from Astarte, on 

 account of the very lengthened front muscular impression, 

 and a shallow mantle sinus ; the large hinge teeth project 

 in the left valve, corresponding to cavities in the right. — 

 Fossil. 



Crassatella. Lam. — Shell equivalve, inequilateral, 

 solid, and heavy, not gaping; 

 hinge very thick, cardinal teeth, 

 two in one valve, one in the 

 other, lateral teeth scarcely seen ; 

 a triangular pit under the bosses, 

 for the internal ligament ; mus- 

 cular impressions very distinct, 

 pallial simple. Animal unknown. crassatena. 

 — 19 species f; also fossil. 



Mature specimens of this shell are very thick; their 

 locality is !New Holland and the southern seas, also the 

 South American coasts. Some species are covered with a 

 strong epidermis, and they are generally rare. 



Cardinia. Agassiz. (Sinemuria De Christol ; Pachy 



Forbes's British Moll. 



| Reeve's Iconica. 



