32; 



HISTORICAL PALAEONTOLOGY. 



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 



Fig. 249. A, Under surface of the skull of Rhinoceros Etniscus, 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.) 



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 indi- 

 genous 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- 



