424 venerinjE. 



surface of the valves is sometimes sulcatecl or transversely 

 striated, but is usually smooth, and the internal margin of 

 the valves is entire. The hinge is generally composed of 

 four diverging teeth in one valve and three in the other, 

 with corresponding pits, and the ligament is external and 

 prominent. The genus includes many recent species, beiug 

 represented in most seas. Australia, China, India, Europe, 

 and Western America afford examples. 



Species of Meretrix. 



casta, Gmel. lusoria, Chem. 



castauea, Lam. lyrata, Sow. 



corpulenta, Gray. mitis, Gray. 



formosa, Sow. inorphina, Lam. 



fusca, Phil. ovum, Hanley. 



graphica, Lam. petechials, Lam. 



grata, Desk. Philippinarura, Hanley. 



hieroglyphica, Conr. triradiata, Gmel. 



impudica, Lam. zonaria, Lam. 

 Lamarckii, Desk. 



Sub-gen. gomphina, Morch. 



Shell sub-triangular, sub-equilateral, slopes nearly straight, 

 ventral edge arcuated. Hinge with three approximate cardinal 

 teeth in one valve, two and a rudimentary one in the other ; no 

 lateral teeth. 



donacina, Chem. 



Genus CA.LLISTA, Poli. 



Mantle-margins plicate, with filaments above the base of 

 the respiratory siphon ; siphons united to their ends, crowned 

 with simple cirrhi. 



