64 



CENOZOIC MAMMAL HORIZONS 



Among Carnivora there now appear in Xortli America representa- 

 tives of all the existing families except (1) Yiverridae and Hysenidse, 

 which never reached America; (2) true Felinge, which first appear 

 in the middle Miocene; (3) Procyonidse, w^hich first appear in the 

 lower Miocene; and (4) Ursidse, which first appear in the middle Pleis- 

 tocene of Xorth America. Among Kodentia is noted the first appear- 

 ance (lower part of the John Day of Oregon) of the distinctively 

 American Haplodontidae; also of the Castoridse (Steneofiher) . Among 

 Insectivora, first appearance of the Talpidse in North America (the 

 Eocene forms with analogous teeth may be ancestral) . Among sur- 

 viving Perissodactyla is noted the presence of numerous larger mem- 

 bers of the Equidse, Tapirid?e, and Rhinocerotidse, the latter family 

 including (a) members of the DiceratheriinaB with very rudimentary 

 horns, and (b) members of the Aceratheriinse of larger size. Artio- 

 dactyla now become very distinctive: Among Oreodontidse Leptau- 

 chenia and Eporeodon appear; among Anthracotheriidae Hyopotamus 

 continues; among CamelidfePro^omer^ic replaces Poehrotlierium; among 

 Hypertragulidse Protoceras (first appearance of this type) is the most 

 distinctive form in the sandstones of South Dakota. 



While the '^Protoceras sandstones" and the clays of the Leptau- 

 chenia zone were being deposited in the Plains Region, there began the 

 volcanic-ash depositions of the John Day formation in the Mountain 

 Region of Oregon. 



OREGON CENOZOIC FORMATIONS. 



RESUME OF THE OREGON DEPOSITS AS A WHOLE. 



The known mammal fauna of Oregon, as determined partly by 

 Cope and Wortman and more precisely as to levels by Merriam and 

 Sinclair, is found on five levels, partly separated by volcanic overflows, 

 as follows: 



Rattlesnake 

 Mascall 



Upper part of John Day 



Middle (fossils numerous) 

 and (?) lower parts of 

 John Day 



= upper Miocene 

 = middle Miocene- 

 = Transition, upper Oli- 

 gocene, lower Mio- 

 cene 



= upper Oligocene, sec- 

 ond phase 



JOHN DAY FORMATION. 



(Figs. 1, 10, 11; PI. I.) 



= Procamelus zone. 

 = Merychippus zone. 

 = Promerycochoerus zone. 



= Diceratherium zone 



The time of the beginning of the John Day deposition appears 

 to corres})ond with that of the close of the Leptauclienia zone in the 

 South Dakota region (fig. 10), namely, the upper Oligocene. 



