PERMO-CARBONIFEROUS VERTEBRATES FROM NEW MEXICO. 



31 



pophyses, laterally. The outer edge of the upper end of the transverse process is 

 just on a line with the outer edges of the anterior and posterior zygapophyses. 

 The articular face runs down to the anterior edge of the centrum. 



The ninth vertebra is the first with a complete neural spine ; this is oval in sec- 

 tion throughout, with the anterior and posterior edges slightly contracted; the 

 upper end is not rugose nor expanded; it terminates in a fiat, smooth face. 



From the tenth to the sixteenth vertebra there is little or no change in form. 

 The maximum width of the neural arches is attained in the tenth and retained to 

 the fifteenth. The upper ends of the transverse processes do not reach beyond 

 the line of the zygapophyses, and beyond the tenth they shorten very rapidly, 

 until in the last of this series they form only very slight prominences on the sides 

 of the centra. The neural spine of the tenth is similar to that of the ninth, but 

 does not exhibit a slight anterior curvature visible in the anterior one ; this curv- 

 ature may be due to accidents in fossilization or may be the last remnant of a 



Fig. 19. — Diasparactus zenos Case. Lateral view of the last eleven presacral vertebrae, X /4- 



decided forward curvature of the spines in the cervical region. On the posterior 

 face of the thirteenth the broken surface shows the edges of distinct hyposphene 

 and hypantrum articulations. The posterior edges of the neural arches of the last 

 vertebra in this series are nearly straight vertically ; they descend almost directly 

 from the base of the neural spines and do not overlap the anterior portion of the 

 succeeding vertebrae, as in Diadectes. The centra are short, without keels on the 

 mid-line, but are somewhat narrowed below. 



The seventeenth vertebra is slightly displaced from the sixteenth, but is held in 

 place by matrix. It shows a very decided change in form from the preceding one. 

 The neural spine is a little higher and the neural arch narrower, with steeply sloping 

 sides. The transverse process is here and in the succeeding vertebras identical in 

 form and condition with those of the type specimen of Diasparactus zenos, No. 4794 

 Am. Mus. Nat. Hist. Cope Coll. The portion of the original description applicable 

 is here repeated.* 



"This new genus and species of the family Diadectidas is characterized by the small 

 size of the centra compared to the height and spread of the neural arches, and the short 

 transverse processes. The whole vertebra is relatively very thin antero-posteriorly, so that 

 while it has the general form of all members of the family, it looks much higher and wider 

 and the small centrum gives it something of a high-shouldered kite-shape, when viewed from 

 the front or rear. The transverse processes are exceedingly short, never extending out 

 beyond the edges of the zygapophyses and in most cases not reaching so far. ' ' 



* Case, Bull. Am. Mus. Nat. Hist. vol. xvii, p. 174, 1910. 



