UNIO. 



For the generic character see plate IV. 



UNIO ELLIPSIS. 



SPECIFIC CHARACTER. 



Shell very oblique, suboval ; summit prominent, as long 

 as the posterior side. 



SYNONYM. 



Unio ellipsis. Lea. Trans. Amer. Philos. Soc. (new 

 series) vol. iii, pi. 4, fig. 4. 



description. 



Shell very oblique, oval-subovatc, ventricose, ponderous : 

 disk convex, lines of growth deeply impressed, somewhat 

 undulating the surface ; yellowish-olivaceous, more or less 

 radiate with green, particularly before ; never spotted ; 

 the old shell uniform brown or fuscous : mar gin regular- 

 ly arquated, even at the anterior tip: siftnmlt prominent, 

 as long as the posterior side: posterior side remarka])ly 

 short: cavity of the hinge membranes profound, much di- 

 lated between the summits and not extending posteriorly 

 beyond the line of the summits ; visible portion triangidar, 



PLATE XIV. II 



