PAPHIID^. 161 



elevated, A-shaped, anterior to the pit, bifid and extending to 

 the inner margin of the cardinal plate ; posterior tooth long, 

 elevated, compressed, oblique; posterior cardinal plate widelj- 

 and profoundly channeled. The left valve only is known. 



Tresus, Gray, 1849. 



Distr, — T. maximus, Midd. (ex, 20.) California. 



Shell oval, oblong, ventricose, gaping posteriorly ; cardinal 

 tooth small, lateral teeth very small, connected with the cardinal; 

 external marginal ligament separated from the cardinal pit by a 

 lamina. 



scHizoTH^RUS, Conrad, 1852. Yery closely allied to Tresus, 

 with a deep channel on either side of the cardinal teeth. The 

 terminations of the siphons are protected by two solid valves. 

 T. Nuttalli, Conrad (ex, 21). 



Eastonia, Gray. 



Distr. — S. rugosa, Gmel. 



Shell thick, oval, radiately ribbed ; cardinal tooth of the left 

 valve compressed ; anterior lateral tooth nearly perpendicular. 



MEROPE, H. and A. Ad., 1852. Shell thinner, radiatel^^ striated 

 or ribbed. U. JSgyptica, Chemn. (ex, 23). 



Labiosa, Schmidt, 1832. 



Syn. — C^'pricia, Gray. Leucoparia, Mayer. 



Distr. — L. lineata, Say (ex, 24). 



Shell oblong, widely gaping and reflected posteriorly ; posterior 

 slope narrow, defined b}^ a carina ; lateral teeth distinct, the 

 anterior one oblique, near the cartilage-pit ; ligament subexternal, 

 marginal, not separated from the cartilage. 



R^TA, Gray, 1849. (Lovellia, Ch. Mayer.) Subcordate, ventri 

 cose, thin, concentrically plicate, subangulate and gaping behind ; 

 cardinal tooth strong ; posterior lateral tooth small. L. canal- 

 iculata. Say (ex, 25). 



Family PAPHIID^. 



Shell subtrigonal, equivalve, close ; ligament lodged in an 

 internal cardinal pit ; cardinal teeth simple, compressed ; lateral 

 teeth rudimentary ; siphons separate, divergent. 



Paphia, Lamarck, 1799. 



Sy7i. — Eryx, Sw. (not Daud.). 



Distr. — 31 sp. West Indies, Mediterranean, Crimea, India, 

 New Zealand, Chili ; sands at low-water. Fossil; Miocene — . 

 F. trigona, Desh. (ex, 26). 



Shell trigonal, thick, compressed, closed ; ligament internal, 

 in a deep central pit ; a minute anterior hinge-tooth, and 1 — 1 



