214 
GEOGRAPHICAL ZOOLOGY. 
[part IV. 
only. The hornless Acerotherium is Miocene only, in both 
countries. Other genera are, Leptodon from Greece, and Hyra- 
codon from Nebraska, both of Miocene age. More than 20 
species of extinct rhinoceroses are known, and one has even been 
found at an altitude of 16,000 feet in Thibet. 
Family 46. — HIPPOPOTAMIDzE. (1 Genus, 2 Species.) 
General Distribution. 
NEOTROPICAL 
Sub-regions. 
Ne arctic 
S ub-regions. 
Paljsarctic 
Sub-regions. 
Ethiopian 
Sub-regions. 
Oriental 
Sub-regions. 
Australian 
Sub-regions. 
Living 
Sfecies. 
1 . 2.3 
Extinct Species. 
The Hippopotamus inhabits all the great rivers of Africa ; a 
distinct species of a smaller size being found on the west coast, 
and on some of the rivers flowing into Lake Tchad. 
Z'ossil Hippopotami. — Eight extinct species of Hippopotamus 
are known from Europe and India, the former Post-pliocene or 
Pliocene, the latter of Upper Miocene age. They ranged as far 
north as the Thames valley. An extinct genus from the Siwalik 
Hills, Merycopotamus , according to Dr. Falconer connects Hippo- 
potamus with Anthracotherium, an extinct form from the Miocene 
of Europe, allied to the swine. 
Family 47. — SUIDzE. (5 Genera, 22 Species.) 
General Distribution. 
Neotropical 
Sub-regions, 
Nearctio 
Sub-regions. 
Pal.earctic 
Sub-regions. 
Ethiopian 
Sub-regions. 
Oriental 
Sub-regions. 
Australian 
Sub-regions. 
- 2.3 — 
- 2 . 3 - 
1 . 2 . 3.4 
1 . 2 . 3. 4 
1 . 2 . 3.4 
1 . 
The Swine may be divided into three well-marked groups, 
from peculiarities in their dentition. 1. The Dicotylime, or 
