292 AFRICAN GAME ANIMALS 



ated eyes, and small brain. The sexual differences in hip- 

 popotamuses consist of greater body size, larger canine 

 teeth, and heavier or more bristle-like hair in the tail tuft 

 in the bull. The difference in the diameter of the canine 

 teeth is so great that skulls can be as readily sexed by the 

 size of the sockets of the tusks as by the teeth themselves. 

 A large number of fossil species of gigantic hippopotamuses 

 are known from the Pliocene and more recent Pleistocene 

 formations of southern Europe, India, Sumatra, Java, and 

 the Mediterranean coast of Africa. Some of these species 

 are scarcely distinguishable by their skull structure from 

 the living amphibius of Africa. Remains of one of these 

 closely allied species of amphibius have been found on the 

 present site of London. Some of the older species of hip- 

 popotamuses of the Pliocene have been separated as a dis- 

 tinct genus owing to the presence of the full number of in- 

 cisor teeth in distinction to the four which characterize the 

 living genus Hippopotamus. Within modern historic times 

 the hippopotamus occurred much more widely distributed 

 than at the present time. Formerly they were found the 

 entire length of the Nile to its delta, but to-day they are 

 absent from the Nile proper north of Khartoum and occur 

 only in its headwaters and tributary streams. At the 

 present time they are greatly diminished in numbers in 

 South Africa, being quite extinct from the Cape district 

 south of the Orange River. They exist to-day, south of the 

 Zambesi, only in a few rivers where they have been afforded 

 strict protection. In equatorial or central Africa they are 

 still abundant from Abyssinia and Senegal south to the 

 Zambesi watershed wherever there are rivers or lakes with 

 sufficient water or swamp vegetation to give them cover. A 

 single living species is known, amphibius, to which several 

 racial or subspecific names have been applied, the earlier of 

 these dating back nearly one hundred years. Racial dis- 

 tinctions have, however, in no case been well established, 

 owing to the small number of specimens preserved in mu- 

 seums and the great individual variation shown by the 

 skulls upon which differences alone have been founded. It 

 is, however, now apparent that there are not only skull 

 differences but slight differences in the body coloration 

 and size as well, which are of a geographical character, and 



