362 
LaUP FOKK EPOCH. 
difference between it and that of the White River beds which underlie it 
in Nebraska and Colorado is far less important than that which distin¬ 
guishes the latter from the older Eocene fauna. The orders of Mammalia 
characteristic of the Eocene are not present in either the White River or 
Loup Fork deposits, which contain, on the contrary, representatives of the 
orders at present existing in the Northern Hemisphere, Africa, and, to a less 
extent. South America. The distinctions between the two later faunae are 
found in subordinate modifications of these orders. It is, however, true 
that Insectivora and Quadrumana, observed in the White River beds, have not 
yet been found in those of the Loup Fork epoch, while Proboscidea, which 
are abundant in the former, are unknown in the White River period. The 
latter distinction is likely to be maintained, as our knowledge of the White 
River fauna is the more complete. The following table represents the pecu¬ 
liarities of the two faunae by contrasting the corresponding forms of each 
order: 
White Eiver. Loup Fork. 
Carnivora. Machaerodus. 
Dinictis. 
Hoplopboneus. 
Bnnaelurus. 
Canis. 
Ampbicyon. 
Artiodactyla. 
Poebrotberinm. 
Hypisodus. 
Hypertragulus. 
Leptomeryx. 
Oreodon. 
Leptaucbenia. 
Agriocbcerus. 
Hyopotamus. 
Elotberium. 
Pelonax. 
Pseudaelurus. 
Mu stela. 
Canis. 
Ampbicyon. 
Tomarctus. 
Aelurodon. 
Bicrocerus. 
Pliaucbenia. 
Procamelus. 
Merycbyus. 
Perissodaciyla. 
Protobippus. 
Hippotberiuin. 
