﻿r.AMPSILlS 199 



is reughened by growth-lines, which near the edge and on the 

 posterior slope often form cuticular laminae; the middle part 

 of the valves is smoother, but marked with one or more small 

 patches of short corrugations, at right angles to the growth- 

 lines, and near the beaks there are some acute, fine, radial 

 wrinkles on the posterior-dorsal slope. 



The beaks are sculptured with two radial series of short, 

 concentric wrinkles separated by a slight depression. The 

 valves are rather thick in the anterior half, becoming abruptly 

 thinner posteriorly. The nacre is purple, fading in the cavity, 

 or bluish-white, becoming purplish and iridescent posteriorly. 

 The pseudocardinal teeth are stout, the anterior one in the left 

 valve wedge-shaped, a rather broad rugose heel below it, the 

 posterior one lying directly under the beak ; lateral teeth double 

 as usual. The right valve has a stout, rugose pseudocardinal 

 with a fossa and then a very small, compressed laminar tooth 

 above it ; lateral tooth single. 



Length 73, height :^y, diam. 23 mm." (Pilsbry.) 



Type locality, Valles River, about three miles below Valles, 

 Mexico. 

 Lampsilis signata Pilsbry, Pr. Ac. N. Sci. Phila., 1909, p. 536, 



pi. XXV, figs. 5, 6; pi. XXVI, figs. 5, 6. 



Lampsiijs semirasa Pilsbry. 



■'The shell is oblong- reniform, the ventral margin being a 

 little concave in the middle or straight, the upper margin 

 strongly arched ; the posterior end is wider in female shells, 

 scarcely so in males. The altitude is contained about i^ times 

 in length, diameter about three times in the length. The sur- 

 face is smoothish except for growth-lines, which are strongest 

 near the lower margin and anterior end. Color various shades 

 of brown, with rather indistinct darker or greenish rays, chiefly 

 on the posterior half. The beaks are low, at the anterior fifth 

 of the length. When perfect they have double-looped, concen- 

 tric sculpture. Valves thin, lined with nacre, which is whitish 

 in the cavity and anteriorly, but pink and very iridescent pos- 

 teriorly, (sometimes suffused with pink throughout, darker 



