24 



GUIDE TO THE FOSSIL MAMMALS AND BIKDS. 



times ; and tlie so-called wild horses now found there are 

 merely escapes from domestication. 



Pier-case The earliest remains of one-toed horses hitherto dis- 



10. covered (Fig. 13, 1) occur in the Lower Pliocene 8i\valik 



Table-case Formation of India {Equus sivalensis, Pier-case 10) ; and 

 they are first found in Europe in the Upper Pliocene, in 

 America in the Pleistocene. Their first appearance in 

 England is in the Norfolk Forest Bed, and their remains are 

 common both in the Pleistocene river-deposits of this country 

 and in caverns (Pier-case 10). These true horses are 

 immediately preceded in Asia, Xorthern Africa, Europe, and 



Table-ease 

 5. 



Fig. 13.— Diagram showing the gradual loss of toes in the fore foot (a) and 

 increase of complexity in the grinding teeth {h) of successive Horse- 

 like Ungulata from Y.\ixoT^e—\iB,riie\\,Hiiracotherium{'^),Anchitlwrium 

 (3), Hipparion (2), and Eqiats (1) f much reduced, but not showing 

 relative size. Digits numbered i, ii, iv. 



Xorth America, Ijy slightly smaller animals, which are 

 already horses in every essential respect, but have a pair- of 

 complete though diminutive side-toes on each foot. The Old 

 World species Itelong to the genus Hipparion (Fig. 13, 2), 

 and remains are exhiljited from India, Persia, Samos, Greece, 

 Italy, Germany, France, Spain, and the Ped Crag of P^ngland. 

 Complete legs, skulls, and other remains from Pikermi, 

 Greece, are especially noteworthy in Pier-case 10. Hipparion 

 has also been recorded from Xorth America, where it 

 immediately succeeds another three-toed horse, Protohippv.s, 

 which is not represented in the collection. 



The ]\Iiocene and Oligocene horse-like animals, both in 

 Europe and in Xorth America, are still smaller than the 



