﻿196 I.AMPSII.IS 



l)ut on the posterior slope tliere is some oblique corrugation in 

 the upper part of the disk. The epidermis is yellow, sparsely 

 marked in the posterior half witii narrow green rays. The 

 very low beaks are eroded in the type specimen. The interior 

 is white, thicker anteriorly, very gradually becoming thinner 

 at the posterior end, where opalescent tints are l>eautifully pro- 

 duced. The cavity of the beak is rather deep. The lateral 

 teeth are short and rather widely separated from the stout car- 

 dinals, which are double and about equally prominent in the 

 left valve. 



Length y8, height 43.5, diam. 22.5 mm." (Pilsbry.) 



Type locality, Casas Viejas River, State of San Luis Potosi, 

 Mexico. 

 Lampsilis novileonis Pilsury, Pr. Ac. N. Sci. Phila., 1909, 



p. 537, pi. XXVII, figs. I, 2, 7. 



"With some resemblance to L. mocteaumensis, this species 

 differs by the slight corrugation of the posterior slope and the 

 more compressed form. Some young specimens, (fig. 7), 

 from the type locality, which seem referable to this species, 

 have the whole valves ornamented with wide, green rays. The 

 beaks have a minute area sculptured with about four concentric 

 wrinkles, which are very weakly bilobed. Outside of this 

 sculptured portion the green rays are very distinct, as in allied 

 species. A faint rib or green stripe radiates from the beak in 

 the middle of the posterior slope, which is in part obliquely 

 corrugated. These specimens measure from 17.5 to 36 mm. 

 long." 



IvAMrsii.is coYENSis Pilsbry. 



"The shell is oblong, with beaks at the anterior fourth of its 

 length ; slightly wider posteriorly, the posterior end sloping 

 above, biangular below ; anterior end rounded ; basal outline 

 moderately curved, convex. There is a rather distinct angula- 

 tion from the beak towards the posterior-basal angle, and the 

 indistinct trace of a ridge to the posterior-median angle. The 

 beaks are low, with minute, recurved tips sculptured with a 

 few coarse, double-festooned wrinkles, the connection b.etween 

 the two curves almost iiUerruptcd. The sculptured portion is 



