2S 
The earliest mammals of the period, those of Eocene age, 
are illustrated by specimens and casts of fossils from the Paris 
basin. 
The mammals of the White River beds of South Dakota 
of Miocene age are illustrated by teeth, skulls and other bones 
of Oreodon, Mesohippus, Elotherium, Dinictis, etc. The Ore^ 
odon, whose skulls occur in great abundance in the Bad Lands 
of South Dakota may be described as “a ruminating hog’’ since 
it combined characters of the hogs and ruminants. It was prob- 
ably about the size of a sheep. 
The Elotherium was also a large hog-like animal of active 
habits. An exceptionally fine skull is shown. 
A* fossil bird’s egg shown is one of few known. 
SIXTH CASE, RIGHT. — Skulls and other bones of Ti- 
‘tanotheriuni from South Dakota. This was a huge, rhinoceros- 
like animal which inhabited South Dakota in Tertiary times. 
The largest individuals must have been about fourteen feet long 
^nd eight feet high. One of the skulls shown, that of T, in- 
gens, is the largest and finest of the genus known. Twelve com- 
plete vertebrae belonging to this individual are also shown, the 
long spinous processes of which are worthy of note as explain- 
ing how the attachment of muscles needed to hold the huge 
head in place was accomplished. 
FLOOR OF HALL. — A restoration of the skull of Elephas 
ganesa, one of seven species of elephants existing during the 
Miocene epoch in India. This species is remarkable for the 
length of its tusks, in this specimen ten feet long. 
Complete skeleton of Mastodon from Southern Michigan. 
This was the earliest of elephant-like mammals, differing from 
the elephant in having a more elongated body, shorter and 
stronger limbs, flatter cranium and less complex molars. The 
grinding surfaces of the molars were more or less tubercular, 
in contrast to the ridges which characterize the teeth of the 
elephant. Hence comes the name, mastodon — nipple tooth. The 
animal probably had no hairy covering to enable it to endure 
a rigorous climate as did the mammoth. It inhabited chiefly the 
temperate regions of the United States, where its remains are 
found in abundance. 
