72 



Bryant Walker 



sculpture feeble, consisting, when developed, of an anterior and posterior 

 loop, the former often wanting; epidermis generally brown, often cloth-like 

 when fresh, rayless or feebly rayed; teeth rather compressed, pseudo-car- 

 dinals frequently imperfect or nearly wanting; laterals remote. JMarsu- 



Fig. 20I 



pium kidney-shaped, consisting of numerous ovisacs occupying the posterior 

 part of the outer gill ; edge of mantle in female slightly lamellar in front of 

 the branchial opening with granulations, but without papillse. Glochidia celt- 

 shaped, with two spines, one at each of the ventral corners. 



Type: Unio alatiis Say, fig. 200. Animal, fig. 201. 



Genus PARAPTERA Ortmann, 191 1. 



Shell large, thin, elliptical or slightly obovate, more or less compressed, 

 winged on the dorsal margin ; beaks low ; epidermis rather smooth, often 

 feebly rayed, dull colored, but usually glossy ; teeth compressed, pseudo- 

 cardinals but feebly and often imperfectly developed ; nacre purplish. Male 

 and female shells,/nearly alike, the latter scarcely swollen at post-basal 

 region. 



Marsupium kidney-shaped, swollen, consisting of many ovisacs occupy- 

 ing the posterior part of the outer gill ; mantle edge of the female slightly 



