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. HIPPOPOTAMID^E. . (1 Genus, 2 Species.) 

 GENEKAL DISTRIBUTION. 



LIVING SPECIES. 



1.2.3 



EXTINCT SPECIES. 



1.2 



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. 



Fossil 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. SUID^. (5 Genera, 22 Species.) 

 GENERAL DISTRIBUTION. 



The Swine may be divided into three well-marked groups, 

 from peculiarities in their dentition. 1. The Dicotylinse, or 



