O. C. Marsh— Vertebrate Lafe in America. 367 
tified in this country below the upper Pliocene, where one 
gigantic species was abundant. In the Post-Pliocene, remains 
of this genus are numerous. The hairy Mammoth of the Old 
World (Elephas primigenius) was once abundant in Alaska, and 
great numbers of its bones are now preserved in the frozen 
cliffs of that region. This species does not appear to have 
extended east of the Rocky Mountains, or south of the Colum- 
bia River, but was replaced there by the American Elephant, 
which preferred a milder climate. Remains of the latter have 
been met with in Canada, throughout the United States, and in 
Mexico, The last of the American Mastodons and Elephants 
became extinct in the Post-Tertiary. 
The order Yoxodontia includes two very peculiar genera, 
Toxodon and Nesodon, which have been found in the Post-Ter- 
tiary deposits of South America. These animals were of huge 
size, sik ocean such mixed characters that their affinities 
are a matter of considerable doubt. They are thought to be 
related to the Ungulates, Rodents, and ae aeeER but as the 
feet are unknown, | this cannot at present be deci 
Macrauchenia and Homalodontotherium are two ae peculiar 
genera from South America, now extinct, the exact affinities 
of which are uncertain. Anoplotherium and Paleotherium, so 
abundant in Europe, have not been found in our orth 
American Tertiary  doposien ‘ithpieh reported from South 
America. 
ica are the Tillodontia, which are comparatively abundant in 
the lower and middle Kocene. These animals seem to com- 
bine the characters of several different groups, viz: the Car- 
nivores, Ungulates, and Rodents. In the genus Tillotherium, 
the type of the order, and of the eee Tillotheride, the skull 
resembles that of the Bears ; the molar teeth are of the 
ungulate type; while the large incisors are very similar to those 
of Roden The skeleton resembles that of the Carn rnivores, 
but the pa | and lunar bones are distinct, and there is a 
third trochanter on the femur. The feet are plantigrade, and 
each had five <> all with long pointed claws. In the 
m fragmentary specimens. 
The Rodents are an ancient type, and their remains are not 
unfrequently disinterred in the strata of our lowest fresh-water 
