326 THE AGE OF MAMMALS 



the main chain to the south. The group reaches the enormous aggregate 

 thickness of 15,000 feet. The clays, sandstones, and conglomerates of 

 which it is composed were probably deposited by the flood plains of great 

 rivers which flowed from the Himalayan chain by the same outlets as their 

 modern representatives ; ' thus there is a close resemblance between these 

 beds and the recent deposits of the flood plain of the Ganges.- 



Here again in the 'Lower Siwaliks' are recorded certain surviving Mio- 

 cene forms such as the giant dogs (Amphicyon), the clawed perissodactyls 

 (Ancylotherium) , supposed entelodonts (Tetraconodon) , and the bear dogs 

 (Hycenardos). In the 'Upper Siwaliks,' or higher Siwalik strata only 

 (Oldham), occurs the Upper Pliocene fauna including the true horse {Equm), 

 the first camels (C. sivalensis), the stegodont elephants (S. insignis, S. 

 ganesa), and the giant tortoises (Colossochelys). Especially modern in 

 these highest strata is the buffalo (Bubalus palceindicus) , closely similar to 

 the buffalo of the Ganges and central provinces of India at the present 

 time. 



The Irawadi Valley of Burma apparently contains only the Upper 

 Siwalik fauna and an intermingling even of Lower Pleistocene types. 



It thus appears probable that the 'survival theory' of the intermingling 

 of Oligocene, Miocene, Lower and Upper Pliocene types in India contains 

 some elements of truth, but has been overstated because of erroneous or 

 incomplete field records. As well observed by Oldham, some of the anom- 

 alies would probably disappear if we knew the horizons. At the same 

 time, the balance of evidence is all in favor of regarding the Siwaliks 

 proper as of Upper Miocene and Lower, Middle, and 

 Upper Pliocene age. While it is not certain that there were Oligocene 

 survivals in the Pliocene of Asia, it is certain that animals which became 

 extinct at the close of the Miocene in Europe, such as the amphicyons, chali- 

 cotheres, dinotheres, the aceratheres, the teleocerine rhinoceroses, the entelo- 

 donts or elotheres, survived in Asia. Otherwise the general law of genetic 

 succession or replacement of more ancient by more modern types prevailed 

 in Asia as in Europe. 



It is premature to attempt to work out the genetic or stratigraphic 

 succession of these mammals, which will furnish one of the most fascinat- 

 ing problems for the British palaeontologist. The fauna is of such deep 

 import in connection with the life of Europe, Africa, and North America, 

 that it is desirable to examine it in some detail. 



General CharoAiters of the South Asiatic Mammals 



A broad survey proves that, as indicated on p. 322, southern Asia 

 was a center of the evolution of the anthropoid apes of the Old World and 



1 Geikie, A., Text-Book of Geology, p. 1021, London, 1893. 



2 Oldham, R. D., A Manual of the Geology of India. Calcutta, 1893. 



