I004 



FRESH-WATER BIOLOGY 



129 (130) Shell large, solid, inflated, subrotund; beak sculpture weak, not 

 continuous with the surface sculpture, which consists of 

 oblique folds; hinge strong and complete. 



Arkansia Ortmann and Walker. 



The type and only species known, A. whederi 0. and W. (Fig. 1499; X a), has recently been 

 discovered in the Oid River, Arkadelphia, Ark. 



Fig. i49y. 



130 (134) Shell elliptic-rhomboid, compressed; pseudocardinals well developed; 

 laterals more or less imperfect or subobsolete. 



Symphynota Lea . . 131 



131 (132, 133) Shell smooth, shining, rayed; teeth delicate; laterals moderately 

 developed. Subgenus Symphynota s.s. 



The type, 5.<'om/'rf55aLea(Fig. 1500; X rl), is one of the common species of the Northern State-S, 

 ranging from New York west to Nebraska and south to Arkansas. Several other species are 

 found in the Atlantic drainage from New \ork to South CaroUna and in eastern Tennessee and 

 northern Alabama. 



Fig. 1500. 



