Fossil Mollusks From the John Day Basin in Oregon 



The collecting of mollusks in the region has apparently been 

 merely an incident to those persons in search of mammal remains 

 and as a consequence definite stratigraphical data have not been 

 recorded. This is unfortunate because it makes it impossible to 

 assign the several species to the geologic subdivisions recognized by 

 the vertebrate paleontologists. No doubt much in the way of 

 correlating this deposit with those elsewhere can be accomplished 

 when the region shall be explored with mollusks the chief objects in 

 mind. 



SPECIES IN THE UNIVERSITY OF OREGON COLLECTION 

 Gastrodonta imperforata Hanna 



Plate 1, figures la and Ib 



One of the four specimens of this species in the collection is 

 almost perfect and is figured in two views because of its super- 

 iority to the type. The axis is completely imperforate and there 

 is a peculiar twist to the columellar wall which recalls Sagda of 

 the West Indies. It may in fact prove to be that the John Day 

 shells belong in or near that genus but the evidence is not con- 

 sidered sufficient to warrant such disposition at present. The 

 shell substance of G. imperforata is exceedingly thin and delicate 

 and the growth striae are uneven and rather coarse. No trace 

 of spiral striation can be found. 



Epiphragmophora antecedens Stearns 



Two imperfect specimens and two fragments have been re- 

 ferred to this species. In no case is the aperture preserved so 

 the identification is somewhat doubtful. 



Epiphragmophora dubiosa Stearns 

 Two imperfect specimens are in the collection. 



Epiphragmophora marginicola (Conrad) 



The finding of a specimen of this, the first John Day shell 

 to be described, is very interesting. Conrad's type was a young 

 shell as shown by his figure and his description was so meager 

 that identification therefrom seemed hopeless. He says "Depres- 



[2] 



