PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 295 



E. lialiotoidea Sowerby, sp., aud E. icalkeri White. The latter species 

 is hirger and proportionally broader than E. icinchelU, aud not properly 

 sessile as the latter species is. E. haliotoidea, as figured by d'Orbiguy 

 in Pal. Fran^aise, t. iii, pi. 478, differs from E. winchelU in being pro- 

 portionately higher in front aud narrower in transverse diameter, and 

 in not having the beaks so much incurved. E. interrupta Conrad, from 

 Mississippi, also belongs to the same section, but that species is de- 

 scribed as having radiating ribs, which ours has not. 



Position and locality. — Cretaceous strata, Collin County, Texas, where 

 it was collected and sent to the Smithsonian Institution by Mr. S. W. 

 Black. The collections of the Institution also contain a fine examj)le 

 sent by Prof. A. Winchell many years ago from Prairie Bluffs, Ala., 

 which is believed to be specifically identical with the form here described, 

 but is proportionally more elongate, has a larger muscular scar, and the 

 umbonal curve is a little more abrupt. The specific name is given in 

 honor of Professor Winchell. 



Genus GERVILLTA Defrance. 



Gervillia mudgeana (sp. nov.). Plate 5, figs. 3 and 4. 



This shell is known only by natural casts in brown hematite of the 

 interior, and a few adhering fragments showing the character of the 

 test. It is moderately large, laterally distorted ; hinge-line compara- 

 tively long, very oblique with the axis of the shell, producing a somewhat 

 prominent posterior alation which is not distinctly defined from the body 

 of the shell ; cartilage-pits in the area of each valve six or seven, as 

 indicated by undulations upon the cast ; beaks placed very near the ante- 

 rior end, beyond which there appears to have been no distinct anterior 

 ear ; beak of the right valve more prominent than that of the other, 

 although the right valve is less convex transversely than the left ; right 

 valve having a somewhat regular and strong longitudinal convexity ; 

 but its transverse convexity is very little in the anterior half, while its 

 posterior half is nearly flat ; left valve nearly straight, or even slightly 

 concave longitudinally along the axis, but very strongly convex trans- 

 versely in all parts of the shell, this convexity being more abrupt along 

 the axis than elsewhere ; and there is also between the axis and the 

 hinge-margin a slightly raised, rounded fold which extends from behind 

 the beak to the posterior margin; adductor muscular impression large 

 and distinct in each valve. A few fragments show the surface to have 

 been marked by the ordinary concentric lines of growth, and also that 

 the test although firm was not massive. 



The dimensions cannot be definitely given, but the largest example dis- 

 covered indicates a length of at least 80 millimeters. 



This shell differs too much from any of the few known Cretaceous 

 species of the genus to need detailed comparison, but it is related to G. 

 subtortuosa Meek & Hayden, Avhich it resembles in being tortuous. It 

 differs, however, in being a proportionally much shorter shell, in the 



