THE PLIOCENE PERIOD. 



339 



and that whilst the winters of the later portion of the Pliocene 

 period were cold, the summers might have been very hot. 

 This would allow of a northward migration of such terrestrial 

 animals during the summer-time, when there would be an 

 ample supply of food and a suitably high temperature, and a 

 southward recession towards the approach of winter. 



The chief palseontological interests of the Pliocene deposits, 

 as of the succeeding Post-Pliocene, center round the Mammals 

 of the period ; and amongst the many forms of these we may 

 restrict our attention to the orders of the Hoofed Quadrupeds 

 (Ungulates}, the Proboscideans, the Carnivora, and the Quad- 

 rumana. Almost all the other Mammalian orders are more 



Fig. 249. A, Under surface of the skull of Rhinoceros Etruacus, one-seventh of 

 the natural size Pliocene, Italy ; B. Crowns of the three true molars of the upper 

 Jaw, left side, of Rhinoceros megarhinus (R, leptorhinus, Falconer), one-half of the 

 natural size Pliocene, France. (After Falconer.) 



or less fully represented in Pliocene times, but none of them 

 attains any special interest till we enter upon the Post-Pliocene. 



