436 ZOOLOGY. 



bodv, very sTiort legs, the belly reaching nearl}^ to the ground ; by an enor- 

 mous head terminated by a broad muzzle. The tail is short ; the ears and 

 eyes small. There ai'e to each foot four nearly equal toes terminated by 

 little hoofs. These animals frequent rivers, and f^ed upon roots and other 

 vegetables. They are stupid and ferocious. The H. aviphihius from 

 southern Africa is represented on pi. Ill, fig. 8. Hippopotami were 

 formerly found throughout Egypt, very abundantly in the Nile, but are con- 

 ilned now to Nubia and to the rivers of central and southern Africa, in 

 Senegal, Zaira, and Gambia. During daytime they keep in the rivers, 

 hidden among marshy grasses. They are good swimmers, and can remain 

 immersed a very long time. When swimming they snort heavily, and 

 exhibit only the snout above the water. They are often met with in flocks 

 of fifty individuals or more. They sleep and lie exposed to the sun in 

 shallow water. The female produces only one young at a time. Hippopo- 

 tami are not dangerous to man, unless attacked by him and wounded. 

 They are killed either by the musket or the harpoon. The Africans make 

 use of the fat and tongue as food, the skin for whips, and the canines (some- 

 times two feet in length) are worked in the same way as the tusk of the 

 elephant, and seem to be a finer article. A small species, H. Uberiensis, 

 is found in the rivers of Liberia, where it is rather common. Fossil species 

 of Hippopotamus are quite numerous in Asia, less so in Europe. Their 

 discovery in America is quite recent. Where they possess onlynfour 

 incisors they form the genus Tetraprotodon^ and when six incisors exist in 

 both jaws we have the genus Hexaprotodon. The species with six incisors 

 in both jaws are more numerous than the others. 



The genus Potamohippus is extinct and little known. It has been esta- 

 blished upon some teeth from the tertiary beds of Germany, resembling 

 much the upper canines of the Hippopotamus, or the lower milk internal 

 incisor of the same animals, but with the difference of being deprived of a 

 farrow at their inner surface. 



The genus Siderotherium was created fi'om a fragment of an upper 

 grinding tooth from the tertiary of Wirtemberg, whose surface is some- 

 what like that of Hippopotamus. 



The genus Elasmotherium was established upon a fragment of the lower 

 jaw, and said to have come from Siberia. Since then one tooth was dis- 

 covered near the Caspian Sea, and a posterior part of a head found on the 

 Ehine has also been referred to it. The molar teeth remind us of those of 

 the rhinoceros ; but the enamelled plate of the interior is more undulated, 

 and presents nearly the same complication as in the teeth of the horse, and 

 perhaps still more that in Hippotherium, or horses of the tertiary era, 

 which sometimes undulate. Their elongated and prismatic form constitutes 

 another analogy with the teeth of the horse. The form of the jaw itself, 

 its size and thickness, indicate a stout animal resembling probably the 

 rhinoceros in its general outlines, and reaching the bulk of the largest 

 species of this genus. Its habits were probably also similar to those of the 

 rhinoceros. 



Fam. 3. Ehinoceeotid^, The genus Rhinoceros is easily distinguished 

 640 



