322 HISTORICAL PAL/EON TOLOGV. 



general characters, possess molar teeth which have their crowns 

 furnished with conical eminences or tubercles placed in pairs 

 (fig. 247, B), instead of having the approximately flat surface 

 characteristic of the grinders of the Elephants. As in the 

 latter, there are two upper incisor teeth, which grow perma- 

 nently during the life of the animal, and which constitute great 

 tusks ; but the Mastodons, in addition, often possess two lower 

 incisors, which in some cases likewise grow into small tusks. 

 Three species of Mastodon are known to occur in the Upper 

 Miocene of the Siwalik Hills of India ; and the Miocene de- 

 posits of the European area have yielded the remains of four 

 species, of which the best known are the M. longirostris and the 

 M. angustidens. 



Whilst herbivorous Quadrupeds, as we have seen, were 

 extremely abundant during Miocene times, and often attained 

 gigantic dimensions, Beasts of Prey (Carnivora) were by no 

 means wanting, most of the principal existing families of the 

 order being represented in deposits of this age. Thus, we find 

 aquatic Carnivores belonging to both the living groups of the 

 Seals and Walruses ; true Bears are wanting, but their place 

 is filled by the closely-allied genus Amphicyon, of which various 

 species are known ; Weasels and Otters were not unknown, 

 and the Hycenictis and Ictitherium of the Upper Miocene of 

 Greece are apparently intermediate between the Civet-cats and 

 the Hyaenas ; whilst the great Cats of subsequent periods are 

 more than adequately represented by the huge " Sabre-toothed 

 Tiger " {Machairodus), with its immense trenchant and serrated 

 canine teeth. 



Amongst the Rodent Mammals, the Miocene rocks have 

 yielded remains of Rabbits, Porcupines (such as the Hystrix 

 primigenius of Greece), Beavers, Mice, Jerboas, Squirrels, and 

 Marmots. All the principal living groups of this order were 

 therefore differentiated in Middle Tertiary times. 



The Cheiroptera are represented by small insect-eating Bats; 

 and the order of the Insectivorous Mammals is represented by 

 Moles, Shrew-mice, and Hedgehogs. 



Lastly, the Monkeys (Quadrumana) appear to have existed 

 during the Miocene period under a variety of forms, remains 

 of these animals having been found both in Europe and in 

 India ; but no member of this order has as yet been detected 

 in the Miocene Tertiary of the North American continent. 

 Amongst the Old World Monkeys of the Miocene, the two 

 most interesting are the Pliopithcciis and Dryopithecus of France. 

 The former of these (fig. 248) is supposed to have been most 

 nearly related to the living Scmnopithcci of Southern Asia, in 



