34 DESCRIPTION OF NEW 



well defined terminal point of the lateral tooth, and in other speci- 

 mens this may he found to be more developed. The anterior lobe of 

 the cardinal tooth is conical. 



Unio glaber. Plate X. fig. 29. 



Testa elliptica, transversa, compressa, glabra, incequilaterali ; valvulis tenuibus ; natibus 

 subprominulis, undulatis ; epidermide lutea, radiatd; dentibus cardinalibus parvis, elevatis^ 

 lateralibus longis ; margarita alba. 



Shell elliptical, transverse, compressed, smooth and shining, inequilateral ; valves 

 thin ; beaks somewhat prominent and undulated; epidermis yellow, radiated ; cardinal 

 teeth small and elevated ; lateral teeth long ; nacre white. 



Hab. Holston River, Ten. Professor Troost. 



My Cabinet. 



Cabinet of Professor Troost. 



Diam. '5, Length -8, Breadth 1*5 inches. 



Shell elliptical, transverse, compressed, polished, somewhat com- 

 pressed behind, inequilateral, substance of the shell thin, somewhat 

 thicker before ; beaks somewhat prominent, with fine, nearly parallel 

 undulations at the tip; ligament short; epidermis smooth, yellow, with 

 numerous fine rays nearly over the whole disk; cardinal teeth small, 

 rather compressed, elevated ; lateral teeth long ; anterior cicatrices dis- 

 tinct; posterior cicatrices confluent; dorsal cicatrices placed in the 

 centre of the cavity of the beaks and under the cardinal tooth ; cavity 

 of the shell shallow ; cavity of the beaks small, angular ; nacre white 

 and iridescent. 



Remarks. — Among the shells brought by Professor Troost from his 

 geological exploration of the eastern part of Tennessee, was this one 

 from the Holston. It is allied to U. iris (nobis), but is not so trans- 

 verse. It differs also somewhat in the rays and beaks, and the epider- 

 mis is more yellow. The epidermis is smooth and polished ; in these 

 respects it resembles the young of U. luteola (Lam.), siliquoideus 

 (Bar.). 



