O. C. Marsh— Vertebrate Infe in America. 355 
cene, have as their most characteristic fossil the genus Oreodon 
and are known as the Oreodon Beds. The upper Miocene, which 
occurs in Oregon, is of great thickness, and from one o its most 
important fossils, Miohippus, may be designated as the Miohip- 
pus Series. The climate here during this period was warm 
Above the Miocene, east of the Rocky Mountains and on the 
Basic: Coast, the Pliocene is well developed, and is rich in 
vertebrate remains. The strata rest unconformably on the 
Miocene, and there is a well marked faunal change at this 
Eocene; and yet in beds of this age, coed over the 
Chalk, fossil mammals of many different kinds abound. 
The enna strange to say, are here few in number, and 
- diminutive in size; and have as yet been identified only by frag- 
mentary specimens, dea most of them too imperfect for accurate 
description. In the higher Eocene deposits, this group is more 
abundant, but still represented by small animals, most of them 
insectivorous, or carnivorous in habit, like the existing Opos- 
sum. From the Miocene and Pliocene, no remains of Marsupials 
have been  desaabiad, From the Post- Tertiary, only specimens 
nearly allied to those now living are known, and most of these 
were found in the caves of South America 
The Edentate Mammals are evidently an American type, 
which belong to animals of this rags and to the genus Moropus. 
