170 HIGH SCHOOL ZOOLOGY. 



From what lias beeu said above, it will be understood that 

 the geographical disti'ibution of the elephants was formerly by no 

 means so limited as it is at tho present day ; for, in addition to 

 the mastodons already referred to, true elephants were abund- 

 ant in Ontario during the pleistocene period, and ranged 

 southwards through the States to Mexico. 



25. Associated with the earliest fossil elephants, there have been found 

 in Miocene strata in Europe remains of a proboscidean of gigantic size 

 (Dinothtrlum), the skull of which measures some live feet in length, and 

 differs from the elephant's, in that some five molars replace the sinf,'le 

 grinder, and that the lower jaws contain the tusks. The conformation 

 of the skull suggests a trunlv like the elephant's, and the bones of the 

 feet, which have also been found, prove it to be referable to this order. 

 No examples of it have been found in America, but in the earlier Eocene 

 strata are found remains of mammals of the size of elephants, and with 

 bones sc»similar, that some nearer alliance is suggested than that they 

 are mere predecessors in time. Their skull and teeth, however, were 

 specialised in a very different direction from that of the Dinotherium, 

 for the former was provided with three pairs of bony cores Hov the at- 

 tachment of horns (whence the name of the principle genus and the 

 order Dinocerata), and the latter were arranged in the following pecu- 

 liar way :^ 



there being no upper and very small lower incisors, while the upper 

 canines were tusk-like, the lower ones small, and the small molars with 

 two transverse ridges. Casts of the cranial cavity of these early Mam- 

 malia show that the brain was very small in size, and low in its type of 

 structure. 



More primitive than Pinoceras and its allies with regard to the teeth 

 are Phenacodus and Coryphodon from the lower Eocene, which have the 

 typical formula § 11, and, in the former case, truly tuberculate teeth. AU 

 the toes are present, the middle one in Coryphodon, however, being 

 distinctly the longer, as in the tapirs. No such primitive hoofed ani- 

 mals persist till the present day, all of them (with the exception of 

 the elephants) having undergone a reduction of the number of toes. 



26. Before we proceed to the typical hoofed animals there is one aber- 

 rant genus (////rox) to be mentioned, which is placed in an order by itself 

 (Hyracoidea). This order includes several species of timid little crea- 



