X CAMEL-LIKE PERISSODACTYLES 267 



three-toed. It was intermediate between a Tapir and a Rhinoceros 

 in size. It has been shown, too, from casts of the interior of the 

 skull, that the cerebral hemispheres are much less convoluted than 

 were those of Titanothrrlnm. 



Related to Palaeosyo^is is another primitive Titanothere, the 

 genus TehnatotJiermm. This is also Eocene, from the Uinta 

 Basin, the uppermost of Eocene strata. The skull of these 

 creatures was rather elongated, and not unlike that of a Titano- 

 there in general aspect. The dentition was complete and the 

 canines not very large. The horns, which acquire so prodigious a 

 development in the later Titanotheres, are just recognisable in at 

 any rate many species of this genus Tdmatotherium, the name 

 being tlius by no means an apt one. Better was that proposed by 

 Dr. Wortman, of Manteoceras or " prophet horned." The horns 

 are small elevations upon the froutals just at the junction of 

 these with the nasals, and, indeed, lying partly upon the hitter 

 l)ones. In T. cornuhim the horns are chietiy Ijorne upon the ^ery 

 long nasals, whose size contrasts with the same bones in the 

 more highly -developed Titanotherium. It appears to be (juite 

 possible that Titanotherium was evolved from the genus 

 Telmato therium} 



SuB-OitDER 9. LITOPTERNA. 



Whether the Macraucheniidae should be considered as a 

 separate group of Ungulata is a matter of dispute. Cope 

 placed them in a special order of Ungulates wdiich he called 

 Litopterna. Zittel, on the other hand, regards them as definitely 

 Perissodactyles. One curious point of resemblance to existing 

 Horses is shown — that is the presence of a pit in the incisor teeth. 

 This matter seems to be so important as to need a placing of 

 these forms in the neighbourhood of the Perissodactyles, even of 

 the Equidae ; it is so peculiar a character, and apparently so little 

 related to any obvious similarity in way of life, that it seems to 

 mark a special affinity. Not so the fact that in Macrauchenia 

 at any rate the orbit was entirely surrounded by bone as in the 

 Horse. We find that condition so frequently acquired in many 

 groups, — a development from an earlier condition where the cavity 

 for the lodgment of the eye is in continuity with the temporal 



^ See Osborn, Bull. Amer. 3fus. A^at. Hist. vii. 1895, p. 82. 



