﻿113 LAMPSIUS 



the larger, and one lateral ; beak cavities shallow, compressed ; 

 muscle scars but slightly impressed ; nacre bluish-white, gener- 

 ally dull, with a purplish or brownish center. Both male and 

 female shells are somewhat obovate, the former round poste- 

 riorly or slightly biangulate. The female shell is moderately 

 produced at the posterior base, and nearly roun<l behind or 

 having a blunt posterior point two-thirds of the way up from 

 the base. 



Length (male) 55, height 35. diam. 17 mm. 



Length (female) 55, height 37, diam. 18 mm. 



Rastern Texas ; east to Enterprise, southeast Alabama ; 

 north possibly to southern Indiana. 



Type locality, Alexandria, La. 

 Unio iiii;:errimus Le.a, Tr. Am. Phil. Soc, X, 1852, p. 268, pL 



xviii, fig. 23 ; Obs., V, 1852, p. 24, pi. xviii, fig. 23. 

 Margaron (Unio) nigerrimtis LiiA, Syn., 1852, p. 31 ; 1870, p- 



49- 

 Lampsilis nigerrimus Simpson, Syn., 1900, p. 551. 



Unio fiiligo Reeve, Conh. Icou.. XVI, 1856, pi. xxx, fig. 159. 

 This species differs from L. lienosa in being thinner, more 

 compressed, more rounded behind, and in being somewhat obo- 

 vate. 



Group of Lampsilis iris. 



Shell rather small, elliptical, moderately solid in front, thin- 

 ner behind ; epidermis covered with dark green, broken rays,. 

 beak sculpture consisting of irregular ridges and corrugations 

 that have a tendency to fall into two loops, which are some- 

 times slightly nodulous below ; nacre bluish, becoming beauti- 

 fully iridescent posteriorly. Animal having the inner branchiae 

 free or united to the abdominal sac ; mantle border often macu- 

 lated and generally in the female having papillae below the mar- 

 supium ; marsupium having a strong, deep sulcus parallel with 

 or near to the base. 



Lamtsilis iKis (Lea). 



Shell long elliptical or long ovate, inequilateral, '^ubinflat- 

 ed, with a low, rounded posterior ridge ; beaks low, compressed, 

 sculptured with verv^ irregular, broken ridges which show a 



