36 DESCRIPTION OF NEW 



Unio Yanuxemensis. Plate XI. fig. 31. 



Testa ellipticd, compressa, transversa, inaquilaterali ; valvulis crassis; natibus subpromi- 

 nulis ; epidermide tenebroso-fuscd ; dentibus cardinalibus magnis ; lateralibus longis subcur- 

 visque ; margarita salmonis colore tinctd, et iridescente. 



Shell elliptical, compressed, transverse, inequilateral; valves thick; beaks some- 

 what prominent; epidermis dark brown; cardinal teeth large; lateral tee(h long 

 and somewhat curved ; nacre salmon colour and iridescent. 



Hab. Cumberland River, Ten. Professor Troost. 

 Cabinet of Professor Troost. 

 Diam. -7, Length 1.2, Breadth 1.9 inches. 



Shell elliptical, compressed, transverse, inequilateral ; substance of 

 the shell thick, thinner behind ; beaks somewhat prominent, and mi- 

 nutely undulated at the tip ; ligament rather short ; epidermis dark 

 brown, apparently without rays ; cardinal teeth large and deeply cleft 

 in the left valve ; lateral teeth long and somewhat curved ; anterior 

 cicatrices distinct ; posterior cicatrices confluent ; dorsal cicatrices pla- 

 ced across the centre of the cavity of the beaks ; cavity of the shell 

 shallow ; cavity of the beaks angular ; nacre salmon colour and very 

 iridescent behind. 



Remarks. — This beautiful shell is another of the fine ones obtained 

 by Professor Troost from Cumberland River. I have peculiar pleasure 

 in calling it after my friend Professor Vanuxem. In its general cha- 

 racters it perhaps most resembles the U. Nashvillianus (nobis), but is 

 more compressed, less transverse, and darker coloured exteriorly. In 

 the nacre, however, the specimen from which this description is made, 

 differs very much, being of an intense salmon colour. In other spe- 

 cimens this character may be found to differ, as colour of nacre is 

 usually in this family very uncertain. 



