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, Poebrotheriwm was “ generalised” in 
many ways. Thus the metacarpals 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 sleghtly 
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.” Fic. TBI Anterior surface of 
Later in historical sequence than axis of Red Deer. x3. 0, 
Poebrotherium, and structurally inter- ee eee ee 
mediate between it and Protolabis, is men for second spinal nerve. 
the Miocene genus Gomphotherium. It  ‘F%0™ Flower's Osteology.) 
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. occidentalis 
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