DESCRIPTION OF NEW 



bluntness of the posterior portion of the shell, as well as by its en- 

 largement towards the basal margin. 



Unio pulcher. Plate III. fig. 6. 



Tesla elUptica, transversa, subcompressa, inoequilaterali ; valvulis subcrassis; nalibus irregU' 

 lariter undulatis ; epidermide lutea, radiis tenebroso-viridibus ; denlibus cardinalibus erectis ; 

 lateralibus prope eorum fines majoribus ; margarita colore caryophylli tincta. 



Shell elliptical, transverse, somewhat compressed, inequilateral ; valves rather thick; 

 beaks irregularly imdiilaled; epidermis yellow, wiih dark green rays; cardinal teeth 

 erect ; lateral teeth enlarged near their termination ; nacre pink coloured. 



Hab. near Nashville, Tenn. Professor Troost. 

 Cabinet of Professor Troost. 

 Diam. -S, Length 1-3, Breadth 2-2 inches. 



Shell elliptical, transverse, somewhat compressed, inequilateral ; sub- 

 stance of the shell rather thick ; beaks rather elevated and irregularly 

 undulated; ligament rather long and straight; epidermis yellow; rays 

 dark green, numerous, diverging from the point of the beak over the 

 whole disk; cardinal teeth large, erect, and disposed to be double in 

 both valves, in the left widely cleft; lateral teeth rather long, some- 

 what curved, enlarged near their termination ; anterior cicatrices dis- 

 tinct; posterior cicatrices confluent; dorsal cicatrices placed in the 

 centre of the cavity of the beaks; palleal impression rather indistinct; 

 nacre beautifully pearly and pink coloured. 



Remarks. — This species belongs to that group of Uniones of which 

 the ci'assus of Say is the type. It differs from the crassus in being a 

 smaller species, in the undulations of the beaks and in the rays. The 

 pink colour, which is more intense at the region of the teeth, is strik- 

 ingly beautiful. The rays of this specimen are very dark, and more 

 defined than in any species I have remarked. I am indebted to the 

 great kindness of Professor Troost for the loan of this shell, to describe 

 and figure. 



