ON THE BONES OF THE HIl'POPOTAMtJS. 381 



The lower canine teeth, v, are enormous, curved into the arc of a 

 circle, triangular in their profile, channelled on their two anterior sur- 

 faces, and worn on almost the entire of their posterior surface. 



The upper, 8, are much shorter, equally triajigular, and mastication 

 produces an ohlique plane, cutting these two anterior surfaces. The 

 posterior is intersected hy a deep longitudinal furrow. 



Moreover, the tv/elve anterior teeth of the hippopotamus are more 

 easily distinguishable by the peculiar texture of their osseous substance. 

 It is extremely hard, and, though ever so well polished, we may observe 

 upon its surface extremely fine and close stria, all concentric with the 

 section of the tooth. Their enamel is moderately thick. 



The hippopotamus has then in all thirty-six teeth : namely, eight 

 incisores, four canine teeth, and twenty-four grinders ; and, counting 

 the anterior sucking teeth, which are cast without being replaced, it 

 may be said to have forty. 



III. The Vertebrcs. 



There are seven cervical vertebrse, fifteen dorsal, four lumbar, seven 

 sacred, and fourteen coccygin ; forty-seven in all. 



The atlas (plate 30, figs. 2 and 3), and the axis (ib. figs. 4 and 3), have 

 very common forms in the large animals. The transverse apophyses 

 of the atlas enlarge towards the back part, so that their anterior 

 angle is obtuse, and the posterior acute. • The superior crest of the 

 axis is long and strongly defined ; it rises higher behind. Its transverse 

 apophysis are slight, and terminate in a small tuberosity. Its odontoid 

 apophy^ses is inserted in a peculiar ring of the atlas, below the 

 medullary canal. 



What may strike as being peculiarly remarkable is, that the atlas 

 and the axis, besides the common articulating surfaces, have each two 

 additional ones, towards the dorsal part. 



The transverse apophyses of the next cervical vertebrae are two- 

 pronged. The upper lobe is horizontal, oblong, and terminates in a 

 vertical surface, which goes on increasing in size as far as the seventh. 

 The lower lobe is almost vertical ; it enlarges very much towards the 

 back, and goes on increasing to the sixth ; but it is completely lost in 

 the seventh. 



The fourth cervical may be seen in plate 30, figs. 6 and 7. 

 The spinal apophyses are compressed and pointed : their length is 

 moderate ; it increases, however, as far as the seventh. 



The body of all these vertebrae is transversely oval, a little convex 

 in front, and concave behind ; it is broader than it is long, without 

 apophyses below, but with a slight crest in the anteriors. On the 

 whole, these vertebree approximate more closely to those of the pig, in 

 the shape and details of the arterial apertures, &c. 



The dorsal vertebrae are furnished with long spinal apophyses, com- 

 pressed and directed backwards ; they increase as far as the third, and 

 then diminish gradually to the ninth, after which they become short, 

 cut into squares, almost equal in height, but always becoming broader 

 from front to rear. The last spinal vertebrte of the back and those of 

 the loins take a more forward direction. 



The surfaces of the articulating apophyses become horizontal as far 



