48 Bryant Walker 



Genus FUSCONAIA Simpson, 1900. 



Shell round, rhomboid, triangular or short elliptical, with a moderate 

 posterior ridge; beaks high and full, curved inward and fonvard, sculp- 

 tured with a few coarse, parallel ridges, which curve upward behind; epi- 



Fig. 152 



Fig- 153 



dermis dark ; surface not sculptured ; hinge plate of moderate width ; pseudo- 

 cardinals strong; nacre white, salmon or purple. 

 All four gills marsupial. 



Type: Unio trigonushes., fig. 152. Animal, (F. ruhiginosa (Lea)), fig. 153. 

 Genus ROTUNDARTA (Rafinesque. 1820) Simpson. 



Fig. 154 



Shell rounded; slightly truncated above in front; posterior ridf^v h v. 

 beaks prominent, curved inward and forward over a strongly marki-l !i.i' 



