22 GUIDE TO THE FOSSIL MAMMALS AND BIRDS. 



Pier-case 8. on the bone where the horn would be attached. The 

 earliest rhinoceroses are the smallest and have the front 

 teeth best developed. Some of them (Hyracodon), as 

 proved by the shape of the back of the skull, could only 

 use their jaws for crushing or chopping their food, and had 

 not acquired the powerful grinding bite characteristic of 

 their modern representatives. Illustrations are exhibited in 

 Pier-case 8 and Table-case 4. 



Pier-case 6. A very peculiar rhinoceros, Elasmotherium sibiricum, 

 with a skull more than a yard in length, lived in Siberia and 

 part of south European Russia in the Pleistocene period. It 

 must have borne an enormous horn, not on the nose, but on 

 a bony prominence in the middle of the forehead above the 

 eyes. Its teeth, though formed on the rhinoceros-plan, are 

 shaped like those of a horse. They have crimped enamel 

 and must have been very effective grinders for a long-lived 

 animal. Plaster casts of the skull and other remains are 

 exhibited in Pier-case 6. 



Pier-ease 8. The Titanotheriidse, of the Eocene and Oligocene periods 

 Case L. j n America, seem to have been closely related to the early 

 rhinoceroses. Some typical remains of the latest genus, 

 Titanotherium itself, are placed in Pier-case 8, and a fine 

 skull is exhibited in a special Case (marked L). The head is 

 shaped like that of a rhinoceros; but the roof of the nose- 

 cavity bears a pair of small bony horns or horn-cores, and 

 the teeth form an almost or quite continuous series in the 

 mouth. The fore foot has four toes, of which the two middle 

 ones are less unequal than in the tapirs ; the hind foot has 

 three toes. Some species attained a very large size, 15 to 

 18 feet in length (Fig. 12). 

 Pier-case The typical one-toed horses (of family Equidse), which 



10 - are only found in a wild state at the present day in Africa 

 and Asia, ranged also over Europe and the whole of North 

 and South America during the Pleistocene period. Some of 

 them, whose bones cannot be distinguished from those of 

 Equus caballus, wandered even into the Arctic Eegions. 

 Most of them belonged to the genus Equus, but a few in 

 South America were peculiar, notably the Hippidium and 

 Onohippidium found in the Argentine Republic. As shown 

 by a plaster cast of the skull in Pier-case 10, the latter genus 

 was characterised by a remarkable development of the nose : 

 it is also known to have possessed unusually short and stout 

 legs. All the American horses seem to have become extinct 

 before the New World was colonised from Europe in historic 



