xlvi. CONCHYLIA— D/rifFi?^. 



53. Anodon. 



1. Cygneus, inesquilateralis, anticS angustato-acuminatus. 



inequilateral, narrowed to a point at the anterior 

 side. 



2. paludosus, suhaquilateralis, antic^ sinuato-suhangulatus. 



nearly equilateral, sinuous and somewhat angular 

 at the anterior side. 



3. Anatinus, antich alatus, umbonihus erosis. 



winged at the anterior side, and eroded about the 

 beaks. 



4. Avonensis, lateribus rotundatis, umbonibms siibterminalibus. 



rounded at the sides, and the beaks nearly terminal. 



54. Unio. 



1. margaritiferus, subarcuatus, epidermide nigra. 



slightly arched, and clothed with a black skin. 

 5.5. Mysca. 



1. Batava, extremitatibus rotundails. 



rounded at both sides. 



2. Pictorum, oblonga, antice acuminata, margine coarctato. 



oblong, pointed at the anterior end, with the 

 margin contracted. 



3. ovata, ovata, margine subarcuato. 



oval, with the margin slightly curved. 



4. solida, crassa subcylindrica, antich acuminata. 



thick somewhat cylindrical, and pointed at the 

 anterior end. 



