OF THE FAMILY OF NAIADES. 433 



thick. The gibbosus is seldom if ever perfectly white ; all 

 the specimens I have seen of this are perfectly so. 



6. Unio CmcuLus. Plate IX. fig. 14. 



Testa circulari, vcntricosd, sitb-(Equilaterali ; valvulis crassis ; natibus 

 prominulis; dentibus cardinalibus lateralibusque magnis; ligamento 

 brevi crassoque ; margarild alba et iridescente. 



Shell circular, ventricose, nearly equilateral ; valves thick ; beaks 

 slightly elevated; cardinal and lateral teeth large; ligament, short and 

 thick ; nacre pearly white and iridescent. 



Ohio at Cincinnati. T. G. Lea. 

 Hab. -{ Monongahela at Pittsburg. T. Bakewrell. 

 Tennessee at Nashville. Prof. Yanuxem. 

 My Cabinet. 

 Cabinet of T. G. Lea. 

 Cabinet of Prof. Vanuxem. 

 Cabinet of P. H. Nicklin. 

 Cabinet of Dr Griffith. 

 Cabinet of W. Hyde. 

 Cabinet of W. Mason. 

 Cabinet of J. Phillips. 

 Cabinet of the Academy of Natural Sciences. 

 Cabinet of Peale's Museum. 



&c. 

 Unio rotundata ? Lamarck. 

 Diam. 1, Length- 1-5, Breadth 1-5 inches. 



Shell round ; posterior basal margin sometimes very slightly 

 emarginate, very ventricose, transversely wrinkled, nearly 

 equilateral ; substance of the shell thick ; beaks elevated, me- 

 dial, and somewhat recurved; epidermis finely wrinkled, 

 shining, satin-like, anterior to the umboniar slope dark brown, 

 posterior light yellow brown ; cardinal teeth oblique, thick, 

 and disposed to be treble in both valves ; lateral teeth short 

 and thick, disposed to be double in right valve as well as left ; 



