340 HISTORICAL PALEONTOLOGY. 



Amongst the Odd-toed Ungulates, in addition to the remains 

 of true Tapirs (Tapirus Arvernensis), we meet with the bones 

 of several species of Rhinoceros, of which the Rhinoceros Etrus- 

 cus and R. megarhinus (fig. 249) are the most important. The 

 former of these (fig. 249, A) derives its specific name from its 

 abundance in the Pliocene deposits of the Val d'Arno, near 

 Florence, and though principally Pliocene in its distribution, 

 it survived into the earlier portion of the Post-Pliocene period. 

 Rhinoceros Etruscus agreed with the existing African forms in 

 having two horns placed one behind the other, the front one 

 being the longest; but it was comparatively slight and slender 

 in its build, whilst the nostrils were separated by an incom- 

 plete bony partition. In the Rhinoceros megarhinus (fig. 249, 

 B), on the other hand, no such partition exists between the 

 nostrils, and the nasal bones are greatly developed in size. It 

 was a two-horned form, and is found associated with Elephas 

 meridionalis and E. antiquus in the Pliocene deposits of the 

 Val d'Arno, near, Florence. Like the preceding, it survived, 

 in diminished numbers, into the earlier portion of the Post- 

 Pliocene period. 



The Horses (Equidce) are represented, both in Europe and 

 America, by the three-toed Hipparions, which survive from the 

 Miocene, but are now verging upon extinction. For the first 

 time, also, we meet with genuine Horses (Equus}, in which 

 each foot is provided with a single complete toe only, encased 

 in a single broad hoof. One of the American species of this 

 period (the Equus excelsus} quite equalled the modern Horse 

 in stature; and it is interesting to note the occurrence of indig- 

 enous horses in America at such a comparatively late geo- 

 logical epoch, seeing that this continent certainly possessed 

 none of these animals when first discovered by the Spaniards. 



Amongst the Even-toed Ungulates, we may note the occur- 

 rence of Swine (Suida*), of forms allied to the Camels (Camel- 

 idce}, and of various kinds of Deer (Cervida} ; but the most 

 interesting Pliocene Mammals belonging to this section is the 

 great Hippopotamus major of Britain and Europe. This well- 

 known species is very closely allied to the living Hippopotamus 

 amphibius of Africa, from which it is separated only by its 

 larger dimensions, and by certain points connected with the 

 conformation of the skeleton. It is found very abundantly in 

 the Pliocene deposits of Italy and France, associated with the 

 remains of the Elephant, Mastodon, and Rhinoceros, and it 

 survived into the earlier portion of the Post-Pliocene period. 



