32 DESCRIPTION OF NEW 



tinct ; dorsal cicatrices placed on the interior part of the plate between 

 the cardinal and lateral teeth ; cavity of the shell small ; cavity of the 

 beaks small and angular ; nacre pearly white and iridescent. 



Remarks. — This pretty little species is one of those for which I am 

 indebted to Professor Troost. In its outline it very closely resembles 

 U. rubiginosus (nobis). It difters from it, however, entirely in the 

 form and size of its cardinal teeth, and in having green interrupted 

 rays. A single specimen only has come under my observation. 



Unio Zeiglerianus. Plate X. fig. 27. 



Testa ellipticd, transversa, inaquilaterali, glabra ; valvulis subcrassis ; natibus subpromi- 

 nulis, undulatis ; epidermide luted, radiata ; dentibus cardinalibus partis ; lateralibus parvis 

 subrectisque ; margarita purpurea et iridescente. 



Shell elliptical, transverse, inequilateral, smooth ; valves rather thick ; beaks some- 

 what prominent, undulated; epidermis yellow, radiated; cardinal teeth small; la- 

 teral teeth small and nearly straight ; nacre purple and iridescent. 



Hab. Cumberland River, Ten. Professor Troost. 



My Cabinet. 



Cabinet of Professor Troost. 



Diam. -6, Length 1, Breadth 1-6 inches. 



Shell elliptical, transverse, inequilateral, smooth, rounded in the um- 

 bonial slope ; substance of the shell rather thick ; beaks somewhat 

 prominent, with fine undulations at the tip ; ligament rather short ; 

 epidermis yellow, with fine green rays on the posterior portion ; cardi- 

 nal teeth small, deeply cleft in the left valve ; lateral teeth small and 

 nearly straight ; anterior cicatrices distinct ; posterior cicatrices conflu- 

 ent: dorsal cicatrices placed in the centre of the cavity of the beaks; 

 cavity of the shell rather shallow; cavity of the beaks angular; nacre 

 purple and iridescent. 



Remarks, — This shell resembles the U. Muhlfeldianus, herein des- 

 cribed, but may be distinguished at once by its being much smaller. 



