﻿382 ANOnONTA 



l)luisii-\vliitc to sky hlue, iridescent licliind, ot'ten slightly thick- 

 ened in front. 



I^ength 52, height ^2, diam. 17 mm. 



Length 55. height 35, diam. iS mm. 



Length 43, height 30, diam. 15 mm. 



iVIexicG, mostly in the Pacific ch-ainage. 

 Anodonta exilior Li:a, Pr. .\c. X. Sci. I'hila., I. 1871. p. 188; 



Jl. Ac. N. Sci. Phila., \1IL 1874, p. 24, pi. vii. fig. 21 ; Obs.. 



XIII. p. 28, pi. VII, fig. 21. — SiMPSox. Syn., 1900, p. 630. — 



VON Marten;^, liiol. Cent.. Amer.. Moll.. 1900. p. 530. pi. 



XL. figs. 8-1 1. 

 Anodonta chalcocnsis Cj^osse and Fischer, J. de Conch., XLI, 



1893, P- i'^- — Fischer and Crosse, Miss. Sci., II, 1894, p. 



522, pi. I. XIV, figs. 7, ya. 



Anodonta cygnca iiiipura (part), I{.\.\'xii!.\i., Proc. Mai. Soc. 



London, X, 1912, p. 125. 



A rather small, smooth, attractive sj)ecies, which is found 

 in the Pacific drainage of Mexico, though it is probable thai it 

 has been found in streams draining into the Gulf of Mexico. 

 Dr. W^illiam Palmer reports that it is cultivated in artificial 

 tanks in Durango and used for j)re]jaring sou]), which he 

 claims is of fine quality. Fischer and Crosse believed that their 

 A. clialcocnsis diflfered from A. exilior, basing their oi)inion 

 chiefly on the fact that it was more elongated than Lea's shell. 

 I have seen a large number of specimens from several localities 

 and there is every degree of form from almost orbicular to 

 rather long obovate. 



.A.NODOXT A Ricii.xRDSoxi von Martcus. 



Shell subtriangular or subrhomboid, rather infiated. inequi- 

 lateral, with a low, sometimes scarcely developed, dorsal wing; 

 posterior slope tnmcated ; beaks low, their .scul])ture concen- 

 tric, undulated bars ; posterior ridge low, somewhat double, 

 ending near the base in a wide biangulation : surface with 

 close, concentric stride and fre(|uent broader ridges; epidermis 



