PERISSODACTYLA. 333 



was elongated, and the brain-cavity was very small, the 

 cerebral hemispheres not extending over the cerebellum, 

 and little or not at all over the olfactory lobes. There is a 

 pair of large bony protuberances or horn-cores placed sym- 

 metrically and transversely upon the maxillary bones in 

 both sexes. The nasal bones are elongated, and overhang the 

 nasal cavity. The dental formula in Brontotheriuin is — 



2—2 1—1 4—4 3 — 3 



% ; c 



pm ^ ; m — =38. 



2—2 1—1 " 3—3 3—3 



The incisors are small ; and the canines are short and 

 not separated from the prsemolars by any diastema, these 

 latter being much smaller than the molars. The premolars 

 show two external connate cusps and two closely -united 

 internal cones, and the upper molars have an essentially 

 similar structure, while the lower molars are of the Palseo- 

 therian type. The chief genus is Brontotherium, with which 

 the Symhorodon and Miohasileus of Professor Cope are more 

 or less entirely synonymous. 



The genera Titanothcrium, Megacerops, and Diconodon also 

 belong to this group.^ 



Fam. 5. Palojotheridcc. — This family comprises a number 

 of remarkable Eocene and Miocene Mammals, which are 

 related closely to both the Tapirs and the Equidm. The 

 ty]3e-genus is Palmotheriuin itself, which abounded under 

 various specific forms in the European area during the 

 earlier portion of the Tertiary period. The Palceotheria 

 possessed feet very much like those of the Tapirs, but 

 there were only three digits to both fore-feet and hind-feet. 

 The skull is also Tapiroid in its character, especially in the 

 prominence of the nasal bones, from which it is deduced 

 with great probability that the nose possessed a short mov- 

 able proboscis. The general form also may be supposed 

 to have been like that of the Tapirs, and the restoration of 

 Palmotlurium magnum given by Cuvier (fig. 634) exhibits 



^ American palaeontologists are by no means agreed as to the number of 

 genei'ic types in the Brontoiheridce, or even as to the names of these. As it 

 is quite impossible for the author to decide this question on its merits, he has 

 adopted the names used by Marsh, who has most fully elucidated the group. 



