602 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



respects it differs from all other species of the genus kuown to me. It 

 perhaps approaches more nearly in general form to B. hyimorum Lin- 

 naeus than to any other living species in the United States : but, besides 

 being much larger, it differs in the proportion of its volutions, espe- 

 cially of the body- volution, as well as in some minior details. 



Fosition and locality. — Judith Eiver group ; — Dog Creek, a tributary 

 ,of the Upper Missouri Eiver, Montana Territory. j 



Physa copei (sp. nov.). — Shell large, elongate-subellipticalj -folu- 

 tions about four ; spire short; body- volution large and moderately in- 

 flated 5 suture not deep ; aperture elongate-subovate in marginal out- 

 line, produced in front ; callus of the inner lip moderately thick. Sul?face 

 marked only by the ordinary faint lines of growth. 



Length 5 centimeters ; diameter of body-volution 2^ centimeters. 



This fine Physa is the largest species known to me except P. plevQma- 

 Us White from the Wahsatch group of Wyoming, Colorado, and Utah. 

 It differs from that species, however, in being proportionally longer, less 

 ventricose, and in having the border of its aperture more iiroduced in 

 front. 



The specific name is given in honor of its discoverer, Prof. E. D. 

 Cope, the distinguished paleontologist. 



Position and locality. — Judith River group ; — south side of the Mis- 

 souri Eiver, near Cow Island, Montana Territory. 



