ANODONTA 



175 



Anodonta Oregonensis, Lea, Or-e-gon-en'-sis, has 

 *a shell oval in outline, rather thin, pearl-tinted, and 

 covered with a dark or greenish epidermis. The 

 oldest parts of the shell, which in this case are at the 

 umbones, are often partially dissolved by the acids in 

 the river-water, leaving the white shell exposed. 

 There are no hinge-teeth. The hinge-line is nearly 

 parallel to the base of the shell, quite different from 

 the last species. The specimens described were 

 gathered in the north, from the Columbia river, near 

 The Dalles, and in the south, from the vicinity of 

 Los Angeles. 



Fig. 148. 



Anodonta NuttalUana, Lea, is very similar to Cali- 

 forniensis, as is also A. Wahlamatensis, Lea. I con- 

 sider them both as only varieties of that species. 



Anodonta angulata, Lea, an-gu-la'-ta, Fig. 148, 

 however, is distinct and has a well-marked form. It 

 is much wider at one end than at the other, and is 

 marked by a sharp angle running obliquely from the 

 umbo to the corner of the shell. Epidermis dark 



