652 STEARNS 



the late Professor Cope a small collection of fossil moUusks. 

 Some two years later Professor Thomas Condon, of the Uni- 

 versity of Oregon, presented to the Geological Survey a small 

 collection of shells which he obtained from the John Day group, 

 at or near the locality from which Professor Cope obtained his 

 specimens. Professor Condon's collection embraced the species 

 which Professor Cope's contained, but no others. The exact 

 locality as given on Professor Condon's label is ' the North Fork 

 of John Day River, Oregon, at the angle of the big bend, longi- 

 tude 119° 40', latitude 44° 50'.' The shells were associated in 

 the same layers with vertebrate remains. 



Dr. White says of these collections: they " contain one, and 

 perhaps two, species of Unio and four or five species of pul- 

 monate gasteropods, which latter I refer to the Helicidae ; but 

 no other invertebrate forms were found associated with them. 

 The John Day deposit being of lacustrine origin one could not 

 expect to find it containing the remains of an extensive mollus- 

 can fauna, as compared with the faunas of marine deposits ; 

 but these small collections do not embrace so wide a variety of 

 forms as lacustrine faunas usually present. No gill-bearing 

 nor palustral pulmonate gasteropods are found among them, 

 and all bivalve mollusks, except the Uniones which have just 

 been mentioned, are also absent. It is therefore quite apparent, 

 from a zoological point of view, that these collections represent 

 only a part, and probably only a small part, of the land and 

 fresh water molluscan fauna which existed in and about the lake 

 in which the John Day strata were deposited. 



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" It is so apparent, from the evidence furnished, that these 

 fossil forms represent the living species ancestrally that one 

 may reasonably make the same use of them, with reference to 

 their genetic history, as if the continuity of that history were 

 known by actual observation. These forms, whose genetic 

 history and specific identity have so evidently been continued 

 in unbroken lines from the John Day epoch to the present time, 

 have endured remarkable vicissitudes of physical conditions as 

 well as considerable geographical dispersion since Miocene 

 time. Some of the changes which have taken place in that 

 region since then are very remarkable. 



" One of the greatest volcanic outflows which the earth has 

 known, covering thousands of square miles with melted rock 

 and forming the great mountains of the Cascade range, oc- 



