290 THE OSTEOLOGY OF ELOTHERTUM. 



outward, as well as downward ; their bases are separated by a broad and deep groove, 

 which is continued upward upon the posterior side of the neural spine. 



The third cervical vertebra also bears a considerable resemblance to that of Hippopo- 

 tamus, differing only in some points of detail. The centrum is short, heavy and moder- 

 ately opisthoccelous, depressed, but increasing posteriorly in vertical thickness. It bears 

 a strong ventral keel, which terminates behind, as in the axis, in a trifid hypapophysis. 

 The pedicels of the neural arch are not, as in the pigs, pierced by foramina for the 

 spinal nerves ; they are low and short, but very thick, and the neural canal is strikingly 

 small. The dorsal side of the arch is short, broad and nearly flat. The neural spine is 

 remarkably well-developed (when the anterior position of the vertebra is taken into 

 account), rising as high as that of the axis. It is rather thin and compressed, although its 

 base occupies the whole fore-and-aft length of the arch. From the base, however, it rapidly 

 tapers upward and terminates in a small, rough tubercle. In Hippopotamus the third 

 cervical lias an even better developed neural spine, not higher, but broader and less 

 tapering than in Etotlierium. The prezygapophyses are large, oblique and somewhat 

 convex ; they are placed very low, so that their inferior margins are separated from the 

 centrum only by narrow notches. The posterior zygapophyses are much larger and 

 more prominent than the anterior pair ; they are also less oblique in position and are 

 raised higher above the centrum, corresponding to the posterior elevation of the neural 

 arch. The transverse process is a eompressed plate, which has no great vertical height, 

 hut is well extended from before backward, exceeding the centrum in length ; the pos- 

 terior portion of the process is thickened and recurved, ending in a rugose hook. The 

 absence of any distinctly marked diapophysial element distinguishes this vertebra from 

 tlu' corresponding one of Hippopotamus and Sus, and in the latter genus the inferior 

 lamella is more slender and rod-like, while the spinal nerves make their exit through 

 foramina in the pedicels of the neural arch. 



The fourth cervical vt rtebra is different, in many respects, from the third. The 

 centrum is somewhat shorter and is l< ss distinctly carinate on the ventral side, but is more 

 decidedly opisthotonus. The neural arch is remarkably short in the anteroposterior 

 dimension, so that the articular faces of the postzygapeqdiyses actually extend forward 

 beneath those of the anterior pair, which gives to the pedicel of the neural arch, when 

 seen from the side, a curiously notched appearance. The neural spine is higher, but 

 more slender and recurved than that of the third cervical. The transverse process i* 

 altogether different in shape from that of the latter. It has, in the first place, a very 

 prominent diapophysial element, which projects outward as a heavy, depressed bar, 

 thickened, rugose, and slightly upcurved at the distal end. In the second place, the 

 inferior lamella is much higher vertieallv, but decidedlv shorter from before backward, 



