1902.] NATURAL SCIENCES OF PHILADELPHIA. 699 



anterior cardinal often obsolete. Lazaria Gray, 1854, and Laza- 

 riella Sacco, 1899, are sjTionymous. 



Section Glans Megerle, 1811. 



Type C. trapezia Linne. 



Valves short, quadrate, convex ; shell small ; the posterior right 

 cardinal often obsolete. 



Subgenus BEGUINA Bolten, 179S. 



Type Chama phreiietica Born, 1780. 



Shell large, mytiliform, subcompressed, with feeble, radial sculp- 

 ture, the umbones terminal, the hinge arcuate and drawn out, the 

 lunule tubular, the posterior cardinals much elongated, the laterals 

 absent. Azarella Gray, 1854, is synonymous. A single ludo- 

 Pacific species is known. 



Genus VENERICAE.DIA Lamarck, ISOl. 



Type V. imbricata Lamarck, Parisian Eocene. 



Shell rounded-trigonal, strongly radially ribbed, lunule minute 

 and deep, escutcheon linear, the hinge with two t ransvei-sely 

 striated cardinals in the left and three in the right valve, a sub- 

 lunular pustule sometimes present in the left valve, bat the laterals 

 absent or obsolete. 



Megacardita Sacco, 1899, is synonymous. 



Subgenus CARDIOCARDITA Anton, 1839. 



Type Cardita ajar Bruguiere. 



Hinge like Venericardia s.s,, pallial line with a broad scar in 

 front of the posterior adductor scar; Agaria (5ray, 1847; Acii- 

 noholus Morch, 1853, and Azaria Tryon, 1872, are synonymous. 



Subgenus COSSMANNELLA Mayer Eymar, 1897. 



Type Cardita cegyptiaca Fraas, Eocene. 



Shell elongate-oval, the cardinal teeth feeble, the ribs slender 

 and distant, the palhal line entire. 



Subgenus CARDITES Link, 1807. 



Type Cardita antiquata Linne (sp. ) ^ C. sulcata Bruguiere. 

 Shell like Venericardia s.s., but the anterior right cardinal 

 absent, the laterals obsolete. 



