FOSSIL LAND SHELLS OF THE JOHN DAY REGION 653 



curred in and near that region since those molhisks lived upon 

 the borders of the John Day Lake. The Glacial epoch has 

 come and gone since then, and an immense subaerial erosion 

 has taken place over the whole region, the extent of which one 

 cannot comprehend without witnessing its results. Not a mam- 

 malian species or genus now exists indigenously upon the 

 North American Continent that existed then, and all other 

 vertebrate forms of continental life have materially changed ; 

 but living descendants of those land snails are thriving to-day 

 in the same region and under the same specific forms that their 

 remote ancestors bore." 



From the interesting observations of Dr. White, the consid- 

 eration of the Pulmonate forms of the Cope and Condon col- 

 lections may properly follow. 



Family HELICID^. 



Genus Epiphragmophora Doering 1875. 



EPIPHRAGMOPHORA FIDELIS ANTECEDENS Stearns. 



(Plate XXXV, figs, i, 2, 3.) 



Helix {Aglaid) fidelis ("^ray (Stearns) Bull. 18, U. S. Geol. Survey, p. 14, 

 pi. Ill, figs. I, 2, 3, 188?. 



These fossil examples at once suggest the well-known and widely 

 distributed living species Helix Jidelis Gray,^ of western North Amer- 

 ica. A careful comparison with the very large geographical suite of that 

 species in the U. S. National Museum, which includes a great number 

 of localities within its known area of distribution, verifies the sugges- 

 tion. The only objection that I can anticipate as likely to be made, 

 is, that the umbilicus in the most perfect of the specimens is closed ; 

 in the example referred to, there is some evidence of mechanical 

 flattening, as if by external pressure, which would have the effect of 

 pushing the reflexed edge of the lip in that part of the shell, over 

 the umbilical cavity to some extent. Aside from this, a critical ex- 

 amination of the large series of recent shells in the National Museum 

 collection, received from the Binney and Stearns collections and other 

 sources, shows a marked range of variation in this feature. While 

 in some specimens the umbilicus is widely open, in others it is so 

 nearly covered that a slightly increased deposit of callus would so 

 completely seal the umbilical opening as to make the shell imperfo- 

 rate. In the museum register the foregoing is numbered 13400. 



iProc. Zool. Society London, July, 1834, p. 67. 

 Proc. Wash. Acad. Sci., December 1900. 



