48 GUIDE TO THE FOSSIL MAMMALS AND BIEDS. 



Pier-case and numerous remains are arranged in Pier-case 22. The 

 c 20 - brain is somewhat better developed than in the Dinocerata, 

 and the teeth are deepened for the effective grinding of dry- 

 vegetation, while the canine teeth are quite small and crowded 

 between the continuous regular series of premolars and 

 incisors. There is one pair of small bony horn-cores above 

 the eye, and there is an immense pair of horn-cores in front, 

 which seem to be the excessively enlarged nasal bones. 

 These horn-cores, like the rest of the large skull, are formed 

 by a mere hollow shell of bone, and the grooves for blood- 

 vessels in their surface suggest that they were originally 

 covered with a sheath of true horn. 



Sub-oedee 5. — Hyracoidea. 



Pier-case The small existing hyraxes of Africa, Arabia, and Syria, 

 20- are the scarcely altered survivors of a group of Eocene 

 hoofed mammals allied to the Amblypoda and Condylarthra. 

 They seem to have originated in the African region, and jaws 

 of one hyracoid (Megalohyrax eocsenus), as large as a donkey, 

 are shown from the Upper Eocene of the Eayum, Egypt 

 (Pier-case 20). Pliohyrax, from the Lower Pliocene of 

 Pikermi (Greece), the Isle of Samos, and Maragha (Persia), 

 must have been equally large. Several fossil hoofed animals 

 found in the Tertiary rocks of South America have been 

 doubtfully associated with this sub-order. 



Sub-oedee 6. — Condylarthra. 



Pier-case These are the small primitive five-toed hoofed animals 



20 - of the Eocene period, which might serve very well for the 

 ancestors of all later Ungulata. They occur both in Europe 

 and North America, but the most satisfactory specimens 

 have been found in the latter country. Phenacodus (Figs. 

 39, 40), of which a plaster cast of a nearly complete skeleton 

 is exhibited in Pier-case 9, is a typical example. Fragments 

 of jaws of Condylarthra are also shown in Pier-case 20. 



Sub-oeders 7-9. — Typotheria, Toxodontia, and 

 Litopterna. 



Pier-cases South America seems to have been separated from the 



Table^case rest of the world during the greater part of the Tertiary 



11, period, and its indigenous hoofed mammals, commonly 



