452 Mesozoic and Cenozoic of North America, [ May 
The primary systems of the Caznozoic Realm are 
Plistocene, 
Pliocene, 
Miocene, 
Eocene. Ve 
Although open to conviction, I have not perceived the neces- 
sity for the term Oligocene for a supposed system between the 
Eocene and Miocene. In America the faunal distinction between 
the latter is so marked as to render a third name, for the present 
at least, unnecessary. 
The characteristic features of the faunz of these divisions are 
as follows: 
Eocene.—Mammatia. Presence of Tillodontia, Tzniodontia, 
Mesony chide, Amblypoda, Condylarthra, and Lophiodontide. 
Absence of Carnivora, Ruminantia,* Proboscidia, Leporidz, Pa- 
læotheriidæ (and Anthropomorpha Europe). Pisces. Presence 
of Osteoglossida and Gonorhynchide. 
Mi0cene.—Mammalia. Presence of Carnivora, of Rhinoce- 
rontide, Leporidz, Ruminantia,* and of Edentata. Absence of 
Tillodonta, Tzniodonta, Amblypoda, and Condylarthra. i 
PLIOCENE.— Presence of extinct families of Mammalia: Casto- 
roididæ, Glyptodontidæ, Megatheriidæ, and Eschatiidæ, and of 
extinct genera, as Holomeniscus and Hippotherium. 
PLISTOCENE.—Mammalia. All families are recent and most 
of the genera; many species also recent. 
EOCENE SYSTEM. 
The Eocene formations of the interior of North America are 
as follows :43 
Uinta, 
Bridger, 
-~ Wind River, 
Wasatch. 
These formations are cany successive in their relations. 
There are two others, contemporary with one or more of these, 
whose characters are due to physical causes. They are the 
 Amyzon beds, 
| 2 ae eg shales. ; 
i They differ from each other in the following faunal peculiarities 
‘ a * Le. , quadritubercular Selenodont Artiodactyla. 
