﻿ANODONTA 377 



post-dorsal slope somewhat truncate ; beaks low but sharp, 

 rising above the dorsal line, with a number of rather strong 

 ridges, which nearly follow the growth lines but sometimes 

 are feebly, doubly looped ; surface nearly smooth ; epidermis 

 shining, greenish or pale olive-green, ashy or pale brownish 

 in the umbonal region, with two or three green rays on the 

 posterior slope; nacre whitish, flesh-colored or lurid puri)lish, 

 a little thicker in front, soft textured and shining. 



Length 75, height 40, diani. 18 mm. 



Length 55, height 33. diam. 17 mm. 



California; east to Utah and Arizona. 



Type locality, Rio Colorado, Cal. 

 Anodonta calif ornicnsis Lea. Tr. Am. Phil. Soc, X, 1852. p. 



286, pi. XXV, fig. 47; Obs.. ^^ 1852, p. 42, pi. XXV, fig. 47.— 



MusGRAVE, Phot. Conch., 1863. pi. t, fig. 4.— Clessin, Conch, 



Cab. Ano., 1874, p. 120. pi. xxxix, figs. 4, 5. — Simpson, 



Syn., 1900, p. 629. 

 Marf^aron (Anodonta) calif ornicnsis Lea, Syn., 1852, p. 47; 



1870, p. 75. 

 Anodon californiensis SowEiUiv. Conch. Icon., XVIL 1870. pi. 



xxviTr, fig. 113. 

 Anodonta cygnea i'mpura (part). Hannibal, Proc. Mai. Soc 



London, X, 1912, p. 125. 



Typically this shell is reasonably distinct, but there are a 

 good many specimens that seem to stand between it and A. 

 nuttalliana. The obovate form, the contraction in front of 

 the low, rounded, posterior ridge, making the outline in front 

 of this decidedly wedge-shaped when viewed from above or 

 below and the delicate glossy texture within and without are 

 characters of importance in this species. 



Anodonta nuttai.ijana Lea. 



Shell typically subrhomboid, a little narrow in front, thin, 

 convex, with a well-developed post-dorsal wing, which meets 

 the truncation of the posterior slope with a decided angle ; 

 posterior ridge scarcely developed though the shell is gener- 

 ally full in this region ; beaks compressed, low, but beginning 



