74 POPULAR CONCHOLOGY. 



V, and has the point near the boss ; valves 

 slightly inequilateral, and gaping a little on 

 each side ; bosses protuberant. Animal, foot 

 sharp, oval, and long. — 33 species recent, and 

 3 fossil. 



The Mactrce live in the sand, and are found 

 in all quarters of the world. This genus in- 

 cludes many rare and beautiful species; the 

 shells exhibit rather a diversity of form, but are 

 generally more or less triangular. 



27. Crassatella. — Shell equivalve, ine- 

 quilateral, solid, and 

 heavy, not gaping ; 

 hinge very thick ; car- 

 dinal teeth, two in one 

 valve, one in the other; 

 lateral teeth scarcely 

 seen ; a triangular cartilage under the bosses ; 

 ligament internal ; muscular impressions very 

 distinct. Animal unknown. — 11 species recent, 

 and 14 fossil.* 



Mature specimens of this shell are very 



* Deshayes divides this genus into two, describing seven 

 or eight species under the genus Crassatella, and the rest 

 with others under a new genus which he names Meso- 

 desma. 



