308 THE ANATOMY OF VERTEBKATED ANIMALS. 



last lumbar articulate with those of the penultimate lumbar 

 and with the sacrum. 



The skull differs from that of the Horse in the absence of 

 any frontal or zygomatic processes in consequence of which 

 the orbit and temporal fossa form one cavity. The nasals are 

 immense, and are separated from the j^remaxillse by a wdde 

 extent of the maxilla on each side. The premaxillse are rela- 

 tively small and reduced to little more than their palatine por- 

 tions. The glenoidal surface of the mandible is transverse 

 and convex. The squamosal sends down an immense post- 

 glenoidal process, which is longer than either the post-tym- 

 panic or the paramastoid. It unites with the post-tympanic 

 to form a kind of false auditory meatus, in the absence of any 

 proper ossified canal of that kind. The periotic and the tym- 

 panic bones are anchylosed, the tympanic being a mere irreg- 

 ular hoop of bone. The pars onastoidea is completely hidden 

 by the junction of the short post-tympanic with the long par- 

 amastoid. The hinder margin of the bony palate is opposite 

 the middle of the antepenultimate molar. 



The mandibular condyle is transverse and convex. The 

 perpendicular portion of the ramus is large, and the coronoid 

 process ascends slightly above the condyle. In a vertical and 

 longitudinal section of the skull, the form of the cerebral cav- 

 ity is seen to be similar to that of the Horse. The inner and 

 outer tables of the bony roof of the skull are separated by 

 great air-cavities. 



The spine of the scapula has no acromion, but gives off a 

 strong recurved process from the middle of its length. 



The radius and ulna are complete, but are anchylosed. 



The carpus has the eight ordinary bones. In the manus 

 the digits ii., iii., iv., are complete, and a bony tubercle articu- 

 lated with the outer facet of the cuneiforme represents digit 

 V. The digit iii. is largest and longest, and its phalanges are 

 symmetrical in themselves ; those of the digits ii. and iv. are 

 not symmetrical in themselves. The terminal phalanges have 

 somewhat the form of the coffin-bone of the Horse. 



The ilia have wide, transversely-directed crests, as in the 

 Horse. The femur is provided with a very strong third tro- 

 chanter. The tibia and the fibula are complete, and the tarsus 

 has the ordinary seven bones. The pulley of the astragalus 

 is not very deeply grooved, and is hardly at all oblique. The 

 facet for the cuboid is very small. The metatarsals resemble 

 the metacarpals in their number and symmetry, but there is 

 no rudiment of the fifth. 



