HIPPOPOTAMI. 
445 
that when the animal is walking on soft mud, the under surface comes in contact 
with the ground. Disproportionately short for the size of the animal, the tail is 
laterally compressed from side to side. The short and broad feet are furnished 
with four well-developed short toes, all of which touch the ground when walking; 
and are encased in rounded black hoofs, of which the middle pair have not their 
inner surfaces flattened; so that the hippopotamus lacks the cloven hoof of the 
pigs and the Ruminants. The toes of the feet are partially connected by webs. 
Although there are a number of bristles on the muzzle, and also a few on the sides 
of the head and neck, as well as at the extremity of the tail, the skin of the hippo¬ 
potamus is naked; it is also rather rough and warty, and of enormous thickness. 
The gigantic mouth of a hippopotamus, when opened to the widest, is one of 
the ugliest sights imaginable, looking like a huge red cavern, from the edges of 
which project the enormous tusks and incisor teeth. The tusks, or canines, are the 
largest of the teeth in the jaws, and are curved backwards in a bold sweep, with 
SKELETON OF HIPPOPOTAMUS. 
their extremities obliquely bevelled off by mutual attrition; they grow through¬ 
out the life of the animal, and their points are directed downwards. The incisor 
teeth likewise grow during the whole period of existence, and thereby differ from 
those of the pigs, which form roots. In the existing species, there are not more 
than two pairs of these teeth, and whereas those of the upper jaw are directed 
downwards, the lower ones project forward in advance of the jaw. The sides of 
the jaws are severally provided with seven cheek-teeth, of which the four premolars 
have subconical pointed crowns, while the broad molar teeth carry four distinct 
columns, which, when worn by use, show on their summits well-defined trefoil¬ 
shaped surfaces of ivory surrounded by a rim of enamel. A peculiarity in the 
lower jaw of the hippopotamus is the presence of a hook-like flange at its hinder 
extremity, as shown in our figure of the skeleton. 
Summarising the result of the foregoing description, it may be observed that 
the hippopotami are entitled to rank as a distinct family on account of the following 
differences from the pigs and peccaries, viz. the broad and expanded muzzle, not 
terminating in a disc ; the subequal size of the hoofs, all of which touch the ground, 
and the absence of flattening in the opposing surfaces of the middle pair; the 
