280 AMERICAN JOURNAL 



DESCRIPTIONS OP NEW MARINE BIVALVE 

 MOLLUSCA. 



BY T. A. COXRAD, 



DQSINIA, Scopoli. 



1. DosiNiA Floridana, Conrad. — Plate 15, fig. 4. 



Description. — Suborbicular. length rather more than the 

 height, moderately thick, lentiform, inequivalve ; posterior 

 margin widely subtruncated, direct, or with a slight inward 

 slope; concentric striae regular, seldom anastomosing towards 

 the ends, becoming obsolete towards the ventral margin; lu- 

 nule depressed, with angulated margins. 



Inhabits Florida Keys, Gulf of Mexico. 



The shell is of a pale straw-color, with a few yellowish- 

 brown irregular linear stains. 



AZARA, D'Orbigny. 



2. AzARA UNDATA, Conrad. — Plate 15, figs. 9, 10, 15. 



Description. — Triangular, rather elongated, ventricose, ine- 

 quilateral; lower valve waved, slightly constricted anteriorly; 

 umbonal slope angular ; upper subrostrated or subcuneiform ; 

 color bluish-white about the umbo and middle of the valves; 

 pale brown generally on the other parts, and hair-like brown 

 zig-zag lines on the anterior, conspicuous above and obsolete 

 below. 



Inhabits Rio de la Plata, S. A. 



This species differs from A. nimbosa, Sowerby. 



CORBULA, Brug. 



3. CoRBULA coNTEACTA, Say. — Plate 15, fig. 12. 



The figure is from a specimen found on the coast of North 

 Carolina. The shell is a true Corhula, not an Azara, as H. 

 and A. Adams suppose it to be. 



