16 PROCEEDINGS OF THE NATIONAL, MUSEUM. vou 60. 



base of each neurapophyses has an antero-internal articuhir surface 

 that contributes to the formation of the cupped end for the recep- 

 tion of the occipital condyle, a middle surface for union with the 

 neuropophyses, and a postero-internal surface for the upper and 

 lateral parts of the odontoid. Above this articular end the neuro- 

 pophyses is constricted fore and aft, above which it is widely ex- 

 panded and arches over the neural canal, meeting on the median line 

 without coalescing. There is no neural spine. Each neuropophyses 

 develops from its upper and hinder border short zygapophyses which 

 articulate with the axis. From its posterior side below a shorter dia- 

 pophyses is developed. 



The odontoid is wider than high and presents a convex face in 

 front, which completes the articular cavity for the occipital condyle ; 

 below is the surface for the intercentrum, and above and behind it are 

 the two articular surfaces for the neuropophyses. The whole pos- 



ox in 



Fig. 13. — Cervical vertebrar of Saniwa knsidens Leidy. Type, Cat. No. 218.5, 

 U.S.N.M. Natural size, at, atlas ; ax, axis ; ax in, axis intercentrum ; h, hyopo- 

 PHYSES ; in, intercentrum of atlas ; 3, 4, 5, 6, 7, cervicals three to seven, hh- 

 spectively. 



terior part is sutured to the centrum of the axis and in part anchy- 

 losed to its hypophyses. 



Axis. — The centrum of the axis measured nearly 15 mm. in 

 length. Much of the spinous process is lacking. The forward part 

 is thin and overhangs the odontoid. On the neural arch there is no 

 trace of a diapophysis. On either side of the neural arch in front are 

 articular surfaces representing the prezygapophyses, and on the pos- 

 terior end the transversely expanded neural arch develops well-defined 

 postzygapophyses. The centrum, as in all Varanids, terminates 

 in a ball behind. Below this ball it sends downward and backward 

 a heavy exogenous process with a cupped end which looks downward 

 and backward for the articulation of the hypophysis which is missing. 

 (See h, fig. 13.) This process is the heaviest of the series, whereas 

 in Varanus they grow progressively heavier from the axis back to 

 the sixth cervical. 



Vertebrae posterior to the axis. — Articulated with the axis was 

 the third, fourth, fifth, sixth, and anterior end of the centrum of 

 the seventh vertrebrae, counting backward from the skull (see fig. 

 13). The vertebrae of Saniwa as compared with those of Varanus, 



