﻿I.AMPSII.IS 



197 



not quite two mm. long. Subsequent growth is marked with 

 growth-lines only, or with a very slight oblique corrugation in 

 places on the posterior slope. The epidermis is smooth, but 

 not glossy, and is shortly and finely lamellose towards the 

 margins. Color, obscure greenish-yellow, indistinctly marked 

 all over with green rays. Near the beaks the rays are very 

 distinct on a light ground. By transmitted light it is light yel- 

 lowish, very profusely marked with green rays. The interior 

 is white and somewhat thick anteriorly, thin, blue and slightly 

 iridescent in the posterior half. The teeth are moderately 

 strong. 



Length 36, height 21, diam. 13.5 mm." (Pilsbry.) 

 Type locality, Coy River, State of San Luis Potosi, Mexico. 

 Lampsilis coyensis Pilsbry, Pr. Ac. N. Sci. Phila., 1909, p. 

 538, pi. XXVII, figs. 3, 4. 



"This may turn out to be a small, rayed variety of L. novi- 

 leonis, yet specimens from 28 to 36 mm. long have every ap- 

 pearance of adult shells. The cardinal teeth in the left valve 

 are stouter and their crests are more united than in L. nozn- 

 leonis. While L. undk'aga, coyensis and noznlconis are closely 

 related species, they seem, with present material, to be distinct." 



IvAMPSILIS UNDIVAGA Pilsbry. 



"The shell is oblong, the altitude about three-fifths of the 

 length, diameter slightly over one-third the length ; solid, dull 

 blackish brown, without rays. The anterior end is rounded, 

 posterior end more or less truncate below, sloping steeply 

 above. Surface of the valves with sculpture of distinct growth- 

 lines, and sometimes having a patch of very indistinct vertical 

 corrugations near the posterior ridge on the most convex por- 

 tion. There are also some fine oblique corrugations on the 

 posterior-dorsal slope near the beaks, when not worn oflf. 

 Beaks low, between the anterior fifth and sixth of the length ; 

 when perfect the tip is acute and sculptured with a series of 

 short folds on the posterior ridge. The interior is fleshy-pur- 

 plish, iridescent posteriorly; nacre in the anterior half is 7'ery 

 thick, posteriorly thin. Cavity of the beaks deep and angular. 



