AND OTHER FAMILIES. 173 



Unio Cooperianus. Plate VIII. fig. 21 



&• 



Testd suborbiciilatd, nonnihil ohllquu, inequilaterd, dimidio postico tuberculatd ; 

 valvulis crassis ; natihiis prominentibus ; dentibus cardinalibus subgrandibus ; 

 luteralibiis subbrevibus, crassis rectisqiie ; margariid albd et carnis colore tinctd. 



Shell suborbicular, somewhat oblique, inequilateral, tuberculated on posterior half ; 

 valves thick; beaks elevated ; cardinal teeth rather large; lateral teeth rather short, 

 thick and straight ; nacre flesh coloured and white. 



Hab. River Ohio. T. G. Lea. 



My Cabinet. 



Cabinet of Mr Cooper. 



Diam. 1-9, Length 2-8, Breadth 3-2 inches. 



Shell suborbicular, somewhat oblique, inequilateral, irregularly 

 tuberculated on the posterior half; substance of the shell thick ; beaks 

 thick and elevated; ligament rather short and thick; epidermis wrin- 

 kled, dark rusty brown; rays scarcely visible; cardinal tooth rather 

 large and widely cleft in the left valve, single and emerging from a 

 pit in the right valve; lateral teeth rather short, thick and straight; 

 anterior and posterior cicatrices both distinct ; dorsal cicatrices situated 

 on the under part of the cardinal tooth ; cavity of the beaks deep and 

 angulated ; nacre flesh coloured and white, the white usually forming 

 a broad border bet^veen the palleal cicatrix and the margin. 



Remarks. — This species very closely resembles, in most of its char- 

 acters, both the verrucosus (Barnes) and pustulosus (nobis). It differs 

 from the first in never being chocolate coloured. It is rarely, I believe, 

 entirely white like the latter. The epidermis is dark, and when rays 

 can be seen on it, they will be found to be pencilled, and not one broad 



this I found a character not perceptible in the eroded one from which the description was 

 made, the beaks being furnished with radiated folds nearly similar to those of the lacteolus 

 and Burroughianus described herein. This character seems to prevail very much in the 

 South American Uniones. Among the numerous species described from North America, none 

 yet have been observed to possess this character. 

 46 



