II 6 NATURAL HISTORY ESSAYS 



hippopotamus is but an absurdly faithful replica 

 of its giant relative, careful examination will 

 demonstrate that the following differences exist 

 between the two : 



1. The face of the pigmy hippopotamus (as 

 compared with the cranium) is relatively smaller 

 than that of H. amphibius, so that the eye of the 

 lesser animal is much nearer the centre of the skull. 



2. The lower jaw of the pigmy hippopotamus 

 carries only two incisors, instead of four, as in the 

 larger species. 



3. The forehead of the Liberian animal is con- 

 vex from before backwards, and also from side to 

 side, but that of the common hippopotamus is 

 concave in both directions. 



4. The orbits of the lesser species are never 

 elevated : but those of the larger one are always 

 prominently developed. 



5. An examination of the dried skulls of both 

 animals will demonstrate that the brain cavity, 

 ear-capsules, and orbits of H. liberiensis are 

 relatively larger than those of H. amphibius. 



These characters are of course best seen by 

 contrasting adult specimens of both animals, but 

 a comparison of a full-grown pigmy hippopotamus 

 with even a calf of the common species, will 

 amply demonstrate the essential differences be- 

 tween the two. An adult H. liberiensis is about 

 the size of a thirteen month old calf of H. amphibius 



