718 BULLETIN UNITED STATES GEOLOGICAL SURVEY 



Position and locality, — Laramie Group, Valley of Bear Eiver, seven 

 miles northwestward from Evanston, Wyoming, and at several jpoints 

 in the vicinity of Mellis Station, Union Pacific Eailroad, near the con- 

 fluence of Sulphur Creek and Bear Eiver. It is associated with Cam- 

 peloina tnacrospira Meek, Unio vetustus Meek, and other fresh-water 

 moUusks, as well as many brackish-water species. 



Genus ODO]!^TOBASIS Meek. 



Odontohasis ? formosa (sp. nov.). 



Shell rather small ; spire equal to about one-half its entire length ; 

 volutions about six, the body one inflated and the distal ones moderately 

 convex, the distal part of each somewhat shouldered, and marked there 

 by numerous small longitudinal folds that become obsolete toward the 

 proximal part j these longitudinal folds are less distinct u]3on the body- 

 volution than upon the distal ones ; upon the latter also there is a small 

 revolving furrow near to, and upon the distal side of the suture, giving 

 those volutions a slightly constricted aspect, but which constriction does 

 not extend upon the body-volution. 



Surface apparently marked only by lines of growth, with the excep- 

 tions already mentioned, and some revolving ridges or lines upon the 

 proximal side of the body-volution, near the beak. 



Length 12 millimeters ; breadth of body-volution 7 millimeters. 



Only one specimen of this species has been discovered, and this is a 

 somewhat distorted cast from the reddish shales of the Laramie Group 

 near its base. Neither the aperture nor the extremity of the beak is 

 shown in the specimen, and I am not entirely satisfied that it belongs 

 to the genus Odontohasis, but its general aspect and observable charac- 

 ters favor that reference, although it bears considerable resemblance to 

 Admetopsis Meek, from the Cretaceous strata at Coalville, Utah. Per- 

 haps a sufficient reason for referring this shell i^rovisionally to Odonto- 

 hasis is the fact that a species of that genus is already known in the 

 Laramie Group, while no other genus is yet known there to which it could 

 be confidently referred. Of the three other, species of Odontohasis yet 

 known, two are from the Fort Pierre Cretaceous Group, a true marine 

 formation, and one from the Laramie Group, near Point of Eocks Sta- 

 tion, Union Pacific Eailroad, Wyoming, a brackish-water formation, 

 and which is there associated with Goniobasis insculpta as well as Ostrea 

 and Anomia. The genus Admetopsis is not yet known to exist in the 

 Laramie Group, nor unassociated with true marine forms. 



When other specimens shall have been discovered, it may prove that 

 the description should be somewhat modified, but it is doubtless quite 

 sufficient for the identification of the species. 



As a rule, the moUuscan remains of the Laramie Group indicate a 

 brackish condition of the waters in which they lived. This species is 

 associated with Melania wyomingensis Meek, which is necessarily re- 



