ANCIENT AND MODERN HIPPOPOTAMUSES 263 



of the head, and especially the great width of the mouth, 

 the prominent position of the eyes and nostrils, the minute 

 ears, bulky body, short and stout limbs, and short tail, 

 are among the most striking external features of the 

 creature. The presence of hoofs (four in number on each 

 foot) shows that the hippopotamus belongs to the great 

 order of hoofed, or ungulate, mammals, and the thickness 

 of its nearly naked hide led the older naturalists to place 

 it among what used to be called the pachyderms. It has 

 been shown, however, by anatomical investigations that the 

 group thus designated, which included such totally different 

 forms as elephants, rhinoceroses, and hippopotamuses, is 

 an entirely artificial one, and that the last-named animals, 

 together with their near relatives the pigs, are much more 

 closely connected with the ruminants. 



If the reader desires to know why zoologists place such 

 very dissimilar-looking animals as the hippopotamus and 

 the giraffe in the same great group, while they sunder 

 from the former the apparently more similar rhinoceroses, 

 it may be replied that this is largely due to the difference 

 in the structure of the feet of the two groups. In that 

 the bones of the skeleton of the two middle toes are 

 symmetrical to a line drawn between them, the hippo- 

 potamuses and pigs resemble the ruminants, whereas the 

 rhinoceroses agree with horses in having the middle toe 

 (which is alone present in the latter) symmetrical in itself. 

 One of the essential characteristics of the ruminants is 

 the circumstance that in the lower part of the leg the 

 two middle toes are supported by a single bone known 

 as the cannon-bone, which consists anatomically of two 

 originally distinct elements welded together, while the 

 supporting bones of the small lateral toes are incompletely 

 developed. If, on the other hand, we examine the skeleton 



