﻿19^^ I.AMI'SII.IS 



The pscudocardinal teeth are stout, otherwise formed as in /,. 

 signata; laterals eurved. 



Lenj^th 54, heiij;ht 33, diani. 19 mm. 



Length 54, height 30, diam. 18 mm. 



Length 50, height 30, diam. 18 mm." (Pilsbry.) 



Type locality, Valles River, two miles above Mecos, Mexico. 

 Lampsilis imdh'aga Pilsury, Pr. Ac. X. Sci. Phila., 1909, p. 



536, pi. XXVI, figs. I, 2, 3, 4; xxvir, fig. 5. 



"This species is closely rehited to L. signata, but the valves 

 are thicker and heavier, the teeth are heavier, and the propor- 

 tions differ. It is apparently related to L. actecormn (Phil.), 

 but that is described as thin, valvulis satis teniiibus," whereas 

 in L. undivaga the valves are quite heavy and strong for a 

 Lainpsilis of this size. 



The nacre is nearly white in a few examples. It abruptly 

 becomes thick, (thin?), in the posterior half of the shell. 

 Young shells are conspicuously rayed with green. 



One young shell from the Valles River at Valles, (pi. xxvii, 

 fig. 5), seems to belong to this species, though I am not quite 

 sure of the identity. It is 41 mm. long, yellowish, nearly cov- 

 ered with green rays, the nacre is pale purple, with a wide, 

 darker purple margin posteriorly." 



Lampsii,is signata Pilsbry. 



"The shell is oblong with subparallel dorsal and ventral bor- 

 ders, twice as long as wide, the diameter contained about three 

 times in the length. The anterior border is rounded, posterior 

 border truncate below, sloping and more or less convex from 

 the truncation to the posterior end of the hinge. In some spec- 

 imens the posterior truncation is indistinct or that extremity 

 may be rounded. The beaks are low and situated near the 

 anterior fourth of the shell's length. Adult shells are black- 

 ish, but by transmitted light numerous green rays may be seen, 

 fading out toward the lower border; antl when unworn the 

 beaks show a pretty pattern of distinct green rays on a pinkish 

 or creamy ground. The surface has but little gloss ; the cuticle 



