FRESHWATER AND LAND SHELLS. 15 



(Gmel.) and luteola (Lam.), (siliquoideus, Barnes). It perhaps most 

 resembles the latter, but differs in being a smaller shell, in being more 

 pearly, and in having the beaks nearer to the anterior margin. It is gene- 

 rally found rayed, but in some individuals the rays are wanting ; none 

 of my specimens have perfect beaks. I have great pleasure in naming 

 it after one of our most experienced conchologists and most assiduous 

 students of this branch of zoology, Mr William Hyde. 



Unio interruptus. Plate VI. fig. 15. 



Testa elUptica, compress a, transversa, inoRquilaterali ; valvulis subcrassis ; radiis interruptis ; 

 natibus compressis; dentibus cardinalibus parvis ; later alibus longis subcurvisque ; margarita 

 alba. 



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

 interrupted; beaks compressed; cardinal teeth small; lateral teeth rather long and 

 curved ; nacre white. 



Hab. Harpeth River, Ten. Professor Troost. 



My Cabinet. 



Cabinet of Professor Troost. 



Diam. -9, Length 1-5, Breadth 2-6 inches. 



Shell elliptical, compressed, transverse, inequilateral, subemargi- 

 nate on the posterior dorsal margin ; substance of the shell some- 

 what thick ; beaks rather prominent, somewhat compressed, undula- 

 ted about the tip ; umbones flattened ; ligament rather short ; epider- 

 mis yellow, rather smooth; rays green, broad, interrupted, radiating to 

 all parts of the margin ; cardinal teeth small, conical, deeply cleft in 

 the left valve ; lateral teeth long, and somewhat curved, enlarged at 

 posterior end ; 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 small and sub- 

 angular; nacre pearly white. 



