NATURAL SCIENCES OF PHILADELPHIA. 53 



a prominent tooth, find in having a pallial sinus. I know of one 

 species only, E. latisulcata, a Miocene fossil. 



ALVEINUS. 



Shell eqnivalvecl, smooth ; hinge of both valves with a central 

 pit or emargination ; right valve with 2 approximate tuberculiform 

 minute teeth, the first immediately under the apex and the other 

 beneath and a little in advance of it ; a lanceolate furrow in front of 

 it ; left valve with 2 tuberculiform teeth situated in respect to each 

 other in a line with the anterior hinge margin; a submarginal 

 channel runs entirely round the valves to the apex; pallial line 

 entire ? 



A. minutus, Conracl, PI. I., fig. 6. Amer. Journ. Conch., vol. i. p. 13S, PI. X., 

 fig, 2. 



A minute shell of the Oligocene period found at Enterprise, 

 Miss. The exterior has much resemblance to that of a ventricose 

 Dosinia. The channel around the submargin of the entire shell 

 is, I believe, an unique character. The figure is greatly enlarged. 

 We have but two specimens of this little bivalve, which is ex- 

 tremely thin in substance. 



PARASTARTE. 



Comparing this minute shell with Goodallia triangularis, the 

 hinge is found to correspond with that of the latter, and therefore 

 P. triquetra, Conrad, (Proceed. Acad. Nat. Sciences, 1862) must 

 be named Goodallia triquetra. 



LATIARCA. 



Shell triangular, thick, capacious ; hinge line narrow medially, 

 broad at the ends ; cardinal plates elevated strongly and rugosely 

 striated transversely, the larger plates descending; medial plates 

 very irregular ; lower margin of posterior cicatrix elevated and 

 acute, area between the beaks with conspicuous grooves angulated 

 under the beaks. 



Latiarca idonea, Conrad, PI. II., fig. 1. Amer. Journ. Conch., p. 289. Eocene. 



The most essential difference between this genus and Idonearca 

 is the want of the internal plate, very prominent in the latter, 

 which is also a much shorter shell, with a broader hinge plate. 



Cucullsea crassalina, Lam., is a fine example of this genus. Des- 

 hayes, Coq. Foss. pi. XXXI., fig. 8, 9. 

 1872.] 



