48 



Bryant WAr,KE;R 



Genus FUSCONAIA Simpson, 1900. 



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

 posterior ridge; beaks high and full, curved inward and forward, 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 trigonnsLeai, fig. 152. Animal, (F. rubiginosa (Lea)), fig. 153. 



Genus ROTUNDARIA (Rafinesque, 1820) Simpson. 



Fig. 154 



Shell rounded; slightly truncated above in front; posterior ridge I"\y 

 beaks prominent, curved inward and forward over a strongly marked !i.i'. 



