﻿I.AMPSU.IS 165 



low ; nacre purplish, thicker in front. The male shell is some- 

 what trmicated at the post-dorsal part and is full in the post- 

 basal region, ending in a blunt point just below the medium 

 line. The female shell, of which I have only seen young 

 specimens, is fuller in the post-basal region than that of the 

 male, and is nearly rounded behind. 



Length 123, height 76, diam. 40 mm. 



Eastern Texas. 



Type locality. Rio Colorado, I'exas. 

 Unio color adocnsis Lea, Pr. Ac. N. Sci. Phila., VIH, 1856, p. 



103 ; Jl. Ac. N. Sci. Phila., Ill, 1858, p. 314. pi. xxxi, fig. 29; 



Obs., VI, 1857, p. 34, pi. XXXI, fig. 29. 

 Margaron (Unio) color ado ensis \^vu\, Syn.. 1870, p. 41. 

 Lampsilis Colorado ensis Simpson, Syn.. 1900, p. 568. 



Probably only a mere variety of purpurata. It is less inflated, 

 lighter colored, and is less solid than that species. I have only 

 seen three or four authentic specimens and hardly feel like 

 making it a variety of purpurata without more evidence. 



Lampsilis rovirosai Pilsbry. 



Shell large, moderately solid, obovate, inflated, with strongly 

 marked, somewhat sulcate growth lines ; epidermis dark brown 

 or blackish, with very fine concentric wrinkles ; beaks moder- 

 ately elevated, full ; ligament large ; posterior ridge rounded 

 and above it on the posterior slope there is a radial depression ; 

 hinge line slightly curved ; left valve with two small, slightly 

 ragged, subtriangular pseudocardinals and two short, heavy, 

 remote laterals ; right valve with two pseudocardinals, the up- 

 per rudimentary, and a high, striated lateral ; anterior scars 

 deep and smooth, the adductors large ; posterior scars large, 

 nearly semicircular ; nacre soft flesh-color in the cavity of the 

 shell, whitish at the border, iridescent behind ; beak cavities 

 moderately deep, with a row of muscle scars running towards 

 the anterior base. Hinge line narrow between the two sets of 

 teeth, and occupied with epidermal matter. 



Length 112, height 72, diam. 45 mm. 



Lagima de Atasta, near San Juan Bautista, Mexico. 



