536 PROCEEDINGS OF THE ACADEMY OF [Nov., 



Lampsilis signata n. sp. PI. XXV, figs. 5, 6. 



The shell is oblong with subparallel dorsal and ventral borders, 

 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 specimens 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 blackish, but by transmitted light numerous green rays may 

 be seen, fading out towards the lower border; and when unworn the 

 beaks shows a pretty pattern of distinct green rays on a pinkish or 

 creamy ground. The surface has but little gloss; the cuticle is rough- 

 ened 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, alt. 37, diam. 23 mm. 



Valles River, " near a small falls about three miles below Valles, in the 

 muddy banks of a pool caused by low water. Feb. 4, 1909. " (A.A.H.) 

 A few smaller specimens were taken in the Moctezuma Kiver, Casas 

 Viejas River and Tampamolon Creek. A young shell with the 

 corrugation unusually well developed is figured, pi. XXVI, figs. 5, 6. 

 Lampsilis undivaga n. sp. PI. XXVI, figs. 1, 2, 3, 4. 



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

 eter 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 indis- 

 tinct vertical corrugations near the posterior ridge on the most convex 

 portion. There is also some fine oblique corrugation on the posterior- 



