250 TAPIRS CHAP. 



Ungulate Phenacodus (see p. 202). In the next stage (an 

 embryo of 25 mm.) the humerus has slightly decreased in pro- 

 portionate length, and has come to be more like that of 

 Hipparion. In both of these embryos it should be noted that 

 the ulna is complete and separate from the radius. In the 

 second of the two it has more distinctly acquired the form which 

 it will possess in the adult. The second metacarpal one of the 

 splint bones of the adult is tipped with a small nodule of 

 cartilage, which is clearly the representative of one or more of the 

 phalanges belonging to that digit. 



Fam. 2. Tapiridae. The Tapirs may be distinguished from 

 the Horse and from the Ehinoceros tribe by a few characters, 

 which are as follows : 



The dentition is generally the full one of forty -four teeth. 

 The premolars in the more ancient forms are unlike the molars, 

 but like them in more recent forms. The molars of the upper 

 jaw have two crests parallel and united by an outer crest. The 

 fore -feet have four, the hind-feet three toes. 



The family is fully as ancient as that of the Equidae, but the 

 specialisation of the toes never advances so far. The modern 

 representatives of the order are, so far as the feet are concerned, 

 in the condition of very early representatives of the equine stock. 

 Nor do the teeth of the Tapir's ever reach the complicated pattern 

 of that presented by at least the modern Horses, or indeed of the 

 Palaeotheres. Apart from this it is not an easy matter to dis- 

 tinguish accurately between these several families, including the 

 Lophiodontidae, which, as already mentioned, is placed nearer to 

 the Tapiridae than to the Palaeotheriidae. Indeed the differentia- 

 tion of these two families, the Tapiridae and the Lophiodontidae, 

 seems to be a matter of the greatest difficulty. The difficulty is 

 well emphasised by the fact that naturalists disagree most 

 profoundly as to the relations of various genera of extinct Tapir- 

 like animals. For Mr. Lydekker the genus Lophiodon includes 

 also the American genera Isectolopkus and Systemodon, which are 

 placed by Zittel in the sub -family Tapirinae as opposed to 

 Lophiodontinae, which contains Lophiodon and Helaletes. The 

 existing Tapirs can be differentiated from the existing Horses with 

 great ease, as the following account of the existing genera will 

 show. 



The genus Tapirus is now met with only in South and 



