3° 



PERMO-CARBONIFEROUS VERTEBRATES FROM NEW MEXICO. 



The third vertebra * has lost the neural spine, but judging from the base the 

 spine was broadly diamond-shaped in section with the anterior and posterior edges 

 somewhat extended as in the succeeding vertebrse of the presacral series. The 

 neural arch is slightly convex, beginning to assume the form of the neural arch in 

 all the Cotylosauria, but is still much narrower than those of the dorsal series. The 

 anterior zygapophyses are injured, but were evidently of good size. The neural 

 canal is, as the specimen is prepared, of relatively enormous size, having a diameter 

 greater than that of the centrum ; this is apparently natural, but if so is a most sur- 

 prising feature. The sides and the bottom of the centrum are concealed by the 

 matrix, but it is apparent that the centrum retains the small size seen in the axis 

 and that there was a large intercentrum. It is a notable fact that throughout the 

 presacral series the accommodation for the intercentrum is largely made by the 

 beveling of the anterior face of each centrum and that there is a much smaller face 

 on the posterior end. The transverse process starts from the side of the anterior 

 zygapophysis near the anterior end and runs downward and forward nearly or quite 

 to the anterior face of the centrum at the lower edge ; this is somewhat obscured in 

 the third vertebra, but is very apparent in those immediately following. The upper 



end of the transverse process stands well out beyond 

 a line connecting the outer edges of the anterior and 

 posterior zygapophyses; in this and the rest of the 

 cervicals the characteristic shortening of the trans- 

 verse process does not appear; it begins at the first 

 of the dorsal vertebrae. 



The fourth to the seventh vertebrae have lost the 

 neural spines, but the bases show that they were all 

 rather slender, with the diamond-shaped section de- 

 scribed above. The neural arches become gradually 

 wider and rounder until on the seventh they have 

 assumed fully the form characteristic of the order. 

 The centra of the sixth and seventh are rather more 

 elongate than the anterior ones, somewhat narrowed on the bottom line, but with- 

 out a distinct keel. The intercentrum between the sixth and the seventh is narrow 

 and shallow, not rising much above the lower edge of the centrum ; this is the form 

 observed in all of the succeeding portion of the column except the immediate pre- 

 sacrals. The transverse processes are still prominent, but decreasingly so, and in 

 each vertebra they originate a little farther back until in the seventh the upper 

 end rises from a point a little anterior to the middle of the neural arch. The 

 articular face for the rib is fiat and runs downward and forward, touching the 

 anterior edge of the centrum near the bottom line, so that if the vertebra is viewed 

 from the lower surface the anterior end is considerably wider than the posterior. 

 There is a break following the seventh vertebra, but as the next vertebra is 

 of the correct size and form, and especially as the vertebra were in position as they 

 lay in the ground, it may safely be assumed that the next in series is the eighth and 

 that the lack of a fit is due to the loss of some small amount of matrix, either in 

 the collection or preparation of the specimen. From the eighth dorsal to the twenty- 

 third caudal, the forty-seventh of the complete series, the contact is preserved or, 

 in the caudal series, recorded from the matrix in cleaning. 



The eighth vertebra is imperfect, having lost the spine and a part of the left side. 

 The neural arch is low and convex, with considerable breadth across the zyga- 



* Williston believes that this may be the fourth or fifth. Case beUeves, from comparison with Dia- 

 dcctes, that it is the third. 



Fig. 1 8. — Upper view of third, fourth, 

 fifth, and sixth cervical vertebra; 

 of Diasparactus zenos, X X- 



