GEOGRAPHICAL DISTRIBUTION AND DESCENT. 



35 



GEOGRAPHICAL DISTRIBUTION AND 

 DESCENT OF THE PROBOSCIDEANS. 



The geographical distribution of the pro- 

 boscideans of the present day may be summed 

 up in a few words. They are entirely con- 

 fined to the warmer parts of the Old World, 

 and while the African elephant inhabits the 

 whole of the mainland of that continent south 

 of the Sahara, the Indian elephant is found 

 everywhere to the south of the Himalayas 

 as far as the frontiers of China, and on the 

 large islands in the south from Ceylon to 

 Borneo and Sumatra. It may be that the 

 elephants from the last-mentioned island form 

 a separate geographical variety, but, if so, 

 this variety is only slightly different from the 

 elephant belonging to the mainland. 



The problem becomes much more com- 

 plicated when we take into account the fossil 

 proboscideans, of which we know with cer- 

 tainty besides the elephants two different 

 genera now quite extinct : the Mastodons 

 with a few tubercled molars, and the Dino- 

 theria with numerous smaller molars, whose 

 crowns have transverse ridges (Zygodonts). 

 To enter more thoroughly into the problem 

 we must study the origin of the Proboscidea, 

 and the relations in which the individual 

 genera stand to each other. 



The true elephants have come down to us 

 from the Miocene period, and in particular 

 the Upper Miocene of India. They are 

 accordingly of comparatively recent date, and 

 are not even known in the contemporaneous 

 strata of other countries. In Europe it is 

 not till the time of the Lower Pliocene that 

 we meet with species which approach the 

 African form in the structure of their molars. 

 The Miocene Indian elephants from the 

 Sewalik Hills, from Ava and Perim, belong 

 to a pretty considerable number of species, 

 whose molars form transitions to the masto- 

 dons through having their enamel folds 

 notched into the form of tubercles. This 



approximation is so close, indeed, that certain 

 species {Elephas Cliftii, E. insignis), forming 

 the sub-genus Stenodon, are considered by 

 some naturalists to be true mastodons. Only 

 in the Pleistocene of the "forest bed" of 

 Cromer, near Norwich, and in the contem- 

 poraneous strata on the mainland of Europe 

 and in North America, are there found 

 elephants whose dentition approaches more 

 nearly to that of the Indian species, and 

 since the African type still continues we find 

 the two still living forms almost everywhere 

 together at that time. But in Quaternary 

 times the species of the African type are for 

 the most part restricted to the regions lying 

 round the Mediterranean Sea, while those of 

 the Indian type, and especially the mammoth 

 {E. primigenius), are spread over the whole 

 of the European mainland and the whole of 

 Asia north of the Altai as far as the Polar 

 Regions. The elephants of the African type 

 {E.priscus, nieridionalis, &c.) died out earlier 

 than the others. The mammoth, as already 

 intimated, survived to be a contemporary of 

 man, and an allied species (E. Columbi) lived 

 in Georgia and Mexico into the Ice Age. 



The molars present so many transitional 

 forms not easy to distinguish that we may 

 fairly infer a progressive development of the 

 species from one another. Since the elephants 

 undertake extensive migrations, we are driven 

 to assume that they gradually extended their 

 domain westwards and northwards from India, 

 becoming meanwhile slightly modified in 

 their forms, and that these migrations re- 

 quired a long interval of time, so that the 

 elephants did not reach the centre and south 

 of Europe till Pliocene, nor the north till 

 Quaternary times. The Miocene deposits 

 of India have yielded species from which the 

 types now living can be derived without 

 difficulty. The African elephant still lived 

 beyond a doubt in Malta, Sicily, and Southern 

 Italy during the Quaternary period. 



Be that as it may, the astounding fact still 

 remains that enormous accumulations of the 



