﻿ril.SP.KYOCf'NCHA 239 



Unio Umauillati var. aliycrus Heude. Conch. Fluv. Nank., Ill, 



1877, pi. XVIT, fig. 37. 



Lcpidodesnw aligero Simi'Son, Pr. V. S. Nat. Mus.. X\nil, 



1896, p. 311 ; vSyn., 1900, p. 587. 



Hende believes this to be a variety of his Unio langnilati, 

 but although he gives no description, the figure is so dififerent 

 from the type that T should think this form worthy of specific 

 rank. The concentric sculpture is much finer than it is in lan- 

 guilati, where it consists of coarse ridges ; the posterior ridges 

 are more strongly curved and the pustules are more distinctly 

 de\'eloped. 



Genus PTLSBRYOCONCHA Simpson, 1900. 



Pilshryoconcha Simpson, v^yn., 1900, p. 587. 



Shell elongated, elliptical, compressed, thin, with a low, pos- 

 terior wing, narrow and rounded in front, nearly straight be- 

 low, expanded at the post-basal region, pointed behind. Beaks- 

 compressed, sculptured with several coarse, low, irregularly 

 concentric undulations, often slightly doubly looped ; surface 

 nearly smooth, shining, yellowish to ashy-brownish, sometimes 

 showing very faint rays ; 'hinge straight or slightly curved, 

 reduced to a mere line, often showing a faint, compressed, 

 smooth tooth in front of the beaks, otherwise edentulous ; 

 nacre brilliant, silvery and iridescent ; muscle scars faint. 

 Animal pure milky-white : lobes of the mantle united into two 

 short siphons. 



Type, Anodotita c.vilis I.ea. 



PiLSBRYOCONCHA LINGU.EFORMIS ( Morelet ) . 



Shell irregidarly obovate or subtrapezoidal, compressed, 

 rather thin, with a moderate posterior wing, behind, which it 

 is obliquely truncated, with a low, rounded posterior ridge ; 

 beaks low, their sculpture consisting of nearly straight ridges, 

 which are almost parallel with the dorsal line ; dorsal line 

 somewhat curved ; surface sculptured with numerous concen- 

 tric growth lines; epidermis ashy to yellow-brown, shining; 



