AND OTHER FAMILIES. 73 



Hab. Harpeth River, Tennessee. Professor Troost. 



My Cabinet. 



Cabinet of Professor Troost, Nashville. 



Diam. 1-4, Length 1-9, Breadth 3-1 inches. 



Shell elliptical, subangular behind, nearly equilateral, inflated, trans- 

 verse ; substance of the shell rather thick ; beaks slightly elevated and 

 vs'ithout undulations at tip; ligament short and thick; epidermis yel- 

 lowish with irregularly interrupted rays over the whole disk; cardinal 

 teeth elevated, double in the left valve and single in the right; lateral 

 teeth enlarged and disposed to be bladed at the termination ; anterior 

 cicatrices distinct; posterior cicatrices confluent; dorsal cicatrices situ- 

 ated along the base of the cardinal tooth and under the plate between 

 the cardinal and lateral teeth ; cavity of the beaks wide and obtusely 

 angulate ; nacre pearly white, extending only far enough to leave a 

 broad horn coloured border. 



Remarks. — This species was among the shells sent to me by professor 

 Troost. To judge from the few specimens I have seen, I should sup- 

 pose it varied much from age as well as locality. One of my speci- 

 mens is old and very large, scarcely presenting a ray. In this state it 

 closely resembles the U. ohovatus (nobis), but is rather more trans- 

 verse. The younger and more perfect specimens approach more 

 closely to the U. crassus (Say), but are more inflated, and differ in the 

 rays, which are broken into irregular spots, not entirely dissimilar to 

 the plumage of the partridge. It has some resemblance to the U. pie- 

 tiis herein described, but is not compressed like that species, and differs 

 in the rays. In some specimens the teeth are disposed to be pinkish. 



Unio PicTus. Plate XI. fig. 32. 



Testa ellipticci, cornjrressd, inscquilaterall ; vulvulis siibtenuibus ; natibus com- 

 pressis et ad apices undulatis ; epidermide luted, radiis tenebroso-viridilnis inter- 

 ruptis ; dentibus cardinalibus parris ; latcralibus longis et subcurvis ; margaritu 

 alba et iridcscentc. 



VOL. V. T 



