﻿27.S N^:l'IIRO^fAIA.S 



concentric sulcalions ; beaks near the anterior end, rather full, 

 their sculpture not observed ; anterior and posterior ends 

 rounded below, subtruncate above ; base line very slightly 

 rounded ; epidermis ^reenish-'brown, with numerous hair-like 

 rays; ]:)seu(locardinals lar_i;e. double in the left valve, consid- 

 erabl}' s])lit up; laterals lonj^' and slraij^ht ; muscle scars im- 

 pressed ; dorsal scars numerous, deep, extending;" from the 

 center of the cavity alon^- the base of the pseudocardinals ; 

 cavity of the shell very shallow; cavity of the beaks shallow; 

 nacre dark i>urp]e, iridescent. 



Length 52. height 28, diam. 14 mm. 



Mexico. 

 Unto perstilcatns Lra, Pr. Ac. N. Sci. Phila., XI, 1859, p. 153; 



Jl. Ac. N. Sci. Phila.., TV, i860, p. 255. pi. xl, fig. 135; Obs., 



VII, i860, ]). 73, pi. XI,. fig. 135. — MusGRAVE, Phot. Conch., 



Mari^arofi (LJnio) persidcatus Lea, Syn., 1870. p. 36. 



Nephronaias persidcatus Simpson, Syn., 1900, j). 596. 



Unio cuprinns persidcatus \'()n M.\rtkns, Wiol. Cent. Am., 



Moll.. 1900, p. 505. 



Dr. Lea states that this species has a sharp, compressed 

 keel on the posterior slope, and that there is a single broad 

 yellow rav in this region, extending from the beak to the mar- 

 gin. The outline of the .shell is almost exactly like that of Char- 

 pentier's Unio rui^idosiis, the only difference being that in Lea's 

 shell the beaks are placed a little farther forward. Charpen- 

 tier's species has four broad, yellowish bands on the posterior 

 slope, alternating- with an equal number of green ones, and has 

 heavy pseudocardinals and shining purple nacre. While I do 

 not feel justified in uniting the two T strongly suspect that they 

 are mere forms of one and the same thing. 



Nephron MAS aucrodon (von Martens). 



Shell long rhomboid, subsolid, scarcely inflated, with feeble, 

 concentric sculpture; beaks moderately full, their sculpture 

 not observed; epidermis dirty olive to brownish, with teeble 

 rays on some young shells; ])seudocardinals small, two in the 



