Vol. 5 J 



Merriam-Sinclqir. — Tertiary Faunas. 



197 



A comparison of the Mascall and John Day faunas brings out 

 a number of important contrasts. With the exception of Lepus 

 and Peromyscus 57 , few genera survived the interval of faunal 

 migration and extinction at the close of the John Day, notably 

 Promerycochoems, Miolabis and Steneofiber. With the repopu- 

 lation of the region, hypsodont horses and large camels adapted 

 to existence on grassy plains appear. With these are associated 

 proboscideans and deer of which no ancestral forms are known in 

 the John Day. Evidently a large proportion of the Mascall 

 fauna came into Oregon after the basalt floods bad ceased, mi- 

 grating from other provinces, where its evolution took place 

 during the time of extravasation of the lava or in even earlier 

 time. 



Age. — Knowlton has referred the Mascall to the Upper Mio- 

 cene, basing this conclusion on the affinities and relationships of 

 the forty or more species of plants confined to this formation, but 

 he remarks that if dependence were placed on the distribution of 

 those species which are not confined to the Mascall, "the tend- 

 ency would be to regard them as not younger than Lower Mio- 

 cene, or even possibly as old as the Upper Eocene.""' 15 

 The Mascall has been correlated by him with the Ellensberg 

 formation 59 . A previous correlation with the auriferous gravels 

 of California is no longer retained. 00 



The Mascall fauna has attained about the same stage of evo- 

 lution as the faunas of the Pawnee Creek and Deep Eiver hori- 

 zons of Colorado and Montana, respectively. Merychippus 

 isonesus is common to all three 01 , while ParaMppus brevidens 

 (Desmatippus crenidens Scott) is common to the Deep Eiver 

 and Mascall. This evidence is deemed sufficient for approximate 

 correlation of the three sets of beds. Both faunal and .strati- 

 graphic evidence favors the reference of the Mascall to the mid- 

 dle or later portion of the Miocene. 



See foot-note 40 on p. 185. 

 58 Knowlton. Fossil Flora of the John Day Basin. Bull. 204, U. R. 

 G S., p. 108. 



M Ellensberg quadrangle, IT. S. G. S. Atlas. Note in text. 

 ,; " Bulletin 204, U. 8. G. S., pp. 107-108. 

 Listed by Matthew from the Deep River. Memoirs Amer. Mus., Vol. 1, 

 p. 374. 



