Synopsis Frksh-Water Mollusca 



73 



lamellar in front of the branchial opening, with crenulations, but not with 

 papillre. Glochidia very small, of suboval shape. 



Fisf. 202 



Type: Uiiio gracilis Bar., fig. 202. 



Genus OBOVARIA Rafinesque, 1819. 



Shell short, oval, rounded or retuse, solid, inflated, thick in front, thin- 

 ner behind, with high beaks, which are sculptured with very faint, irregular, 

 often broken and slightly nodulous ridges, which show a tendency to fall 

 into two loops, the posterior often open behind; epidermis dull, brownish, 

 silky or cloth-like, rarely rayed, rays indistinct ; female shell but slightly 

 inflated in the post basal region, commonly having a shallow furrow or a 

 flattened area at the posterior end ; pseudo-cardinals solid ; stumpy ; laterals 

 short, club-shaped. Marsupium kidney-shaped, projecting far below the 

 edge of the gill and occupying the posterior portion of the outer gills. 



Key to the subgenera of Obovaria. 



Shell retrorse to short ova!, beaks high and central Obovaria s. s. 



Shell elliptical, beaks anterior Pseudoon. 



