xi ANCESTRY OF CAMELS 289 



period, and for a long time after, there were no types referable to 

 the Camelidae in the Old World. Though a Camel in many 

 features of its organisation, Poebrotherium was " generalised " in 

 many ways. Thus the rnetacarpals and metatarsals were not 

 fused to form a cannon bone, and the two lateral digits were 

 represented by splint rudiments of metacarpals and meta- 

 tarsals. The dentition was complete. The skull though 

 distinctly Tylopodan, also shows more generalised characters. 

 Thus the orbit is not quite, though nearly, completed by bone. 

 In the Camel it is quite closed. The nasal bones are much 

 longer, reaching nearly to the end of the snout. The odontoid 

 process of the axis vertebra is not spout -like as in existing 

 forms, but cylindrical, though slightly 

 flattened upon the upper surface. The 

 scapula is described as being more like 

 that of the Lama than of the Camel, 

 though variations occur which approxi- 

 mate to the Camel. The brain, judging 

 of course from casts, has those sulci 

 " which are common to the whole series 

 of Ungulates, and closely resemble those 

 of a foetal Sheep." 



* FIG. 151. Anterior surface of 



Later in historical sequence than axis of Red Deer. x|. o, 

 Poebrotherium, and structurally inter- ^ a ^ ; ; ^ E 



mediate between it and ProtolablS, is men for second spinal nerve. 

 .1 TIT- /y -L J.T, TJ- (From Flower's Osteology.) 



the Miocene genus Gomphothenum. It 



shows an advance in structure upon Poebrotherium, in that the 

 orbit is completely encircled by bone, though the posterior wall 

 is thin ; the lower canines instead of being incisiform are curved 

 back as in later Camels, and separated by a wide diastema from 

 the preceding and the succeeding teeth. 



Later in age than Poebrotherium is Protolabis, a Tylopod in 

 which the full number of teeth is still retained ; its skull 

 presents no particular changes from the Poebrotherine type ; the 

 nasals, however, are somewhat shortened. 



Later still in point of time is Procamelus. In this form we 

 have apparently an ancestral stock, whence both Camels and Lamas 

 were derived. The upper incisors are as in existing forms, but 

 the first and second persist for a somewhat longer time. The 

 skull shows two well-marked types of structure ; in P. occidentalism 



VOL. x u 



