of Tin-, i \mii.\ in NAIAD! - 433 



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

 the specimens 1 have seen <>|' this arc perfectly so. 



(i. Unio Cinnus. Plate IX. fiir. I l 



.-• 



Testa circuhiri. ventricosd, sub-tsquilateraK; valvul%3 craasia ; natibxu 

 prominulis; dentibua cardinalibua lateralibuaque magma; ligomento 

 brevi crosaoque; margarila alba et irideacente. 



Shell circular, vcntricoso. nearly equilateral; valves thick; beaks 

 ghtly elevated; cardinal and lateral teeth large: ligament, short ami 



thick ; nacre pearly white and iridescent. 



COlii.. al Cincinnati. T. G. Lea. 

 Hah. j Monongahela at Pittsburg. T. Bakewell. 

 ^Tennessee at Nashville. Prof. Vanuxem, 

 My Cabinet. 

 Cabinet of T. G. Lea. 

 Cabinet of Prof. Vanuxem. 

 Cabinet of P. II. Nicklin. 

 Cabinet of Dr Griffith. 

 Cabinet of W. Hyde. 

 Cabinet of W. Mason. 

 Caliinct of J. Phillips. 

 Cabinet of the Academy of Natural Sciences, 

 Cabinet of Peak's Museum. 



&c. 

 Unto rotvndata? Lamarck. 

 Diam. l. Length \~>. Breadth L -5 inches 



Shell round: posterior basal margin sometimes very slightlj 

 emarginate. very ventricose, transversely wrinkled, nearli 

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

 dial, and somewhal recurved; epidermis finely wrinkled. 

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

 posterior light yellow brown ; cardinal teeth oblique, thick, 

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

 and thick, disposed to be double in right valve as will as lift ; 



