IV.] PERISSODACTYLES. 165 



may be noticed, however, that Bovidce are much more numerously 

 represented in Eastern than in Western Arctogaea ; the latter area 

 having only the genera Bos, Ovibos, Ovis, and Haploceros, each 

 with a single species confined to the more northern portions of 

 the continent ; the last genus being peculiar to this area. 



We now pass to the perissodactyle, or odd-toed ungulates, 

 which while agreeing with the artiodactyle section in the inter- 

 locking arrangement of the bones of the wrist and ankle joints, 

 and the pulley-like upper surface of the astragalus bone in the 

 latter, differ by the third or middle toe and its supporting meta- 

 carpal or metatarsal bone being symmetrical in itself, and larger 

 than the lateral ones, when such are retained. In this suborder 

 the family of the tapirs (Tapiridce), although now mainly Neogaeic, 

 with one outlying Malayan species, was formerly widely spread in 

 northern Arctogaea, fossil remains belonging to the single existing 

 genus Tapirus being abundant in the Pliocene of Europe, although 

 none appear to have been recorded from North America. In 

 both Europe and America there occurs, however, the ancestral 

 genus Protapirus ; its remains having been obtained in the former 

 area from the upper Oligocene phosphorites of France, and in the 

 latter from the nearly equivalent Uinta beds. Possibly a doubtful 

 form {Palceotapirus) from the middle Eocene of France should 

 also be included in the same family. The Uinta and Bridger 

 deposits have also yielded a more or less nearly allied form known 

 as Isectolophus, which apparently also occurs in the European 

 Eocene, where it has been described as Lophiodon. Indeed, in our 

 view, both this genus, and the still earlier American Systemodon, 

 which appears to have been the earliest known representative of 

 the tapiroid stock, may be included in the family Lophiodontidce, 

 where we should also place the ancestral types of the horses. In 

 this family the genus Lophiodon, as now restricted, seems to have 

 been confined to the Eocene of Europe, where it died out without 

 giving rise to descendants, the same being the case with the 

 allied Eocene genus Helaletes^. The well-known Hyracotherium, 

 which was an animal of the size of a fox first described from 

 the London Clay but subsequently recorded from the North 



1 Recorded from Europe by Osborn and Wortman, Bull. Amer. Mus. 

 Vol. vii. p. 360 (1895). 



