UNIO.— Plate LW. 



tral margin somewhat incurved, beaks rather promi- 

 nent, lunule obscure, nacre whitish, cardinal teetli 

 transverse, not large. 

 UuPi-y, Moll. T. et PI. France, p. fi49. pi. 27. f. 16. 

 Hah. .Arcachon, Western France. 



The front extremity is angular above, and rounded be- 

 low ; the hinder side gradually tapers to a rounded peak. 

 The umbonal ridge is not prominent ; the pearly white of 

 the interior is, for the most part, stained here and there 

 with livid olive. 



Species 359. (Mus. Hauley.) 



Unio PowELLll. Uh. testa obhngd,m.odlci iiuequilaterali, 



mbveidricosii, nitide fusco-flavida. concolore, Icevigatd, 



anti.ci perangiidd, rotinidatti, pustice obtusismiid et 



mill turn latiore ; Diargine dorsaU unlice decUvi, jioslic'e 



suiacclioi, marguie ventraU in medio subretuso, pos- 

 iice arcuato, margaritd albidd, dentibus cardinalibus 

 laciidatis. 

 Powell's Uxio. Shell oblong, moderately inequilateral, 

 subventricose, of an uniform glossy brownish-yellow, 

 not sculptured ; front extremity very narrow, round- 

 ed ; hinder extremity much broader, very blunt ; front 

 dorsal edge sloping, hinder one rather elevated ; ven- 

 tral margin somewhat indented in the middle, arched 

 behind, nacre whitish, cardinal teeth jagged. 

 Lea, Obs. on Unio, vol. v. p. 26. pi. 19. f. 25. 

 Hai. Saline river, Arkansas, N. .Vinerica. 



The valves are rather large and strong, with their um- 

 boes, which are almost always eroded, not pai-ticularly 

 prominent. The pearly interior is stained with yeDowish 

 olive in the umbonal cavity; the hinge-margin is rather 

 narrow, ami the nmlional ridge but little projectinu. 



