﻿258 NriPHRONAlAS 



not prominent and niucb eroded. Nacre white. Hinge heavy. 

 Ritjht valve with two nnequal pseudocardinals, (the upper 

 compressed, small: the lower trio^onal. thick, grooved), and 

 one lateral comparatively short, slightly curved. Left valve 

 with two pseudocardinals. the anterior oblique, quite thick, pro- 

 jecting, grooved, the posterior large. i)roniinent, grooved and 

 two lamelliform laterals. Cicatrices of the anterior adductor 

 mu.'^cles deep, grooved ; those of the posterior adductors super- 

 ficial. Ligament brown. 



Length jy, height ^2. diam. 30 mm." (C. & F.) 

 Type locality. Goatzalcoalcos, State of \'era Cruz. Mexico. 

 Unio compntatus Crosse and Fischer, Jl. de Con., 1893. XLT, 

 p. 295. — Fischer and Crosse, Miss. Sci. Mex., Moll.. IT. 



1894, p. 60 T, pi. I.XVII. figs. 2. 2(7. 



"By its ornamentation, U. compntatus resembles U. sapotol- 

 cnsis Lea ; but that species, of smaller size, is relatively thick- 

 er, more inflated, especially in the middle, and the cardinal 

 tooth in the left valve is very heavy. The shells of U. com- 

 pntatus of the same size are thin and the hinge delicate." 



This species was accidentally omitted in making up the 

 Synopsis. 



Group of Nephronaias airryi. 



»Shell triangular-ovate, bluntly pointed in front and biangu- 

 late behind, considerably inflated, irregularly sulcate ; untbonal 

 region moderately developed ; beaks sculptured with fine, ir- 

 regular ridges, which have a tendency to fall into two rounded 

 loops ; pseudocardinals slightly compressed, ragged ; laterals 

 having feeble, oblique striation : front part of the shell some- 

 what thickened : posterior part thinner ; nacre dull, whitish. 



Animal unknown. 



Nephron Ai.-xs averyi (Lea). 



Shell elliptic rhomboid, inflated, very solid, with a moder- 

 ate, double posterior ridge ending in a slight biangulation 

 behind, bluntly pointed in front midway up from the base ; 

 beaks rather high and full, badly eroded in the only .shells 

 seen; .surface somewhat conceiitricallv sulcate. .scarcely shin- 



