﻿ANODONTA 4OI 



rays, with three broad ones at the posterior ridge. The color 

 changes remarkably in the old shells, being ashy or tawny 

 with a decidedly smoky tint and often widely banded with 

 darker color. The nacre is remarkably brilliant, more so per- 

 haps than in any other Anodonta, and it has a very rich, silvery, 

 iridescent sheen. Young shells in unfavorable situations are 

 sometimes colored like the old ones. 



Group of Anodonta zvoodiana. 



Shell oval, inflated, sometimes narrowed in front, pointed 

 behind, and often a little produced at the posterior base, slight- 

 iy winged in the post-dorsal region ; beaks full, sculptured 

 with numerous strong, concentric ridges, which are either 

 straight in the center of the disk or slightly doubly looped. 

 There is often a faint posterior ridge, which may be double, 

 making the shell biangulate behind ; dorsal scars one or two 

 under the beaks; muscle scars irregular. 



Animal having the gills large, equal in size, rounded below, 

 free the greater part of their length from the abdominal sac, 

 somewhat wrinkled ; marsupium occupying the entire outer 

 gills, forming thick, brown pads when filled ; palpi large, sub- 

 elliptical, free from the mantle a long way ; mantle having a 

 wide, thickened edge ; branchial opening crowded with dark 

 papillae; anal opening with no papillae, but having purple 

 ridges inside ; superanal opening closed nearly its whole length. 



Anodonta woodiana (Lea). 



Shell irregularly elliptical, ovate or obovate, subinflated, gen- 

 erally rather strong, with a low. sometimes slightly double, 

 posterior ridge, which ends behind on the median line ; beak i 

 full, generally but slightly elevated, their sculpture a number 

 of parallel ridges, which spread a little behind. These ridges 

 are sometimes nearly straight, or they may be a little curved 

 or feebly doubly looped; dorsal line curved, bounding a win? 

 behind, and generally ending in an angle in front ; dorsal slo]ie 

 trvmcated, the line often incurved ; post-ventral part of the shell 



