TERTIARY MAMMALIA. 177 



principally in size and the polydactyl character of the feet. Among 

 the even-toed ungulates we find the hippopotamus, the true swine, 

 deer, giraffe, and musk-deer, and, of the hcUow-horned ruminants, 

 the antelopes — the sheep, goats,* and oxen being still absent, al- 

 though some of the antelopine forms would seem to effect a transition 

 between the true antelopes and goats. The Proboscidea comprise, 

 in addition to the true elephant (which, however, as a Miocene ani- 

 mal is known only from the deposits of the Siwalik Hills of India, 

 now frequently referred to the Lower Pliocene, or Mio-Pliocene), 

 the Mastodon, and the aberrant Diuotherium, which was provided 

 in its lower jaw with two prominent recurved tusks. The Carnivora 

 have yielded representatives of the cats— the true Pelis and the 

 related sabre-tooths (Machairodus, Dinictis), the most formidable 

 of all known recent and extinct Carnivora — the weasels, civets, 

 hyenas (with the true hyena), and seals. The dogs are represented 

 by the genus Canis itself, and the more primitive Amphicyon, 

 through which a transition is effected to the ursine Hyaenarctos, 

 and to the Pliocene true bears. Finally, the Primates have yielded 

 several genera, as Semnopithecus, Pliopithecus, and Dryopithecus, 

 the last referable to the group of the anthropoid or highest apes, 

 and fully equalling in size the human species. 



Passing on to the Pliocene period, the mammalian fauna makes 

 a still further approximation to that of the present day in the in- 

 troduction of a number of modern types that had not hitherto made 

 their appearance, or only just appeared. Thus, we have here the 

 camel (in India), the ox, true bear (in Europe), and horse, in addi- 

 tion to most of the types that have been enumerated as belonging 

 to the Miocene period, and it may be broadly stated that the ma- 

 jority of the genera of this period are such as still exist, although 

 the species are in most cases distinct. The regions where Tertiary 

 mammals have been studied are principally the United States, Eu- 

 rope, and India, between whose faunas there is a well-marked cor- 

 respondence. While certain of the animal groups referred to are 

 found in the one region and not in the other, and are therefore 

 specially restricted, it may be said that approximately the same 

 groups are represented. throughout, although the date of their ap- 

 pearance, or of that of their individual components, may be different 

 for the different countries. Thus, in the Upper Miocene, or older 



* Capra Perimensis, from the island of Perim, is possibly a Miocene form. 

 13 



