20 AMPHIBIA AND PISCES OF THE PERMIAN OF NORTH AMERICA 



"In the axis, the hypophysis is a large ridge with a horizontal truncate 

 edge. The costal heads of the diapophysis are not split to the base of the 

 latter and the superior is the more robust (extremities broken off). Centrum 

 concave posteriorly, and on each side of hypopophysis with reticulate sur- 

 face. A short zygantropophysis; zygantrum not large. Exposed summit of 

 zygosphen (nearly equal neural arch) without neural spine. In both the axis 

 and other cervical vertebrse, the superior diapophysis is connected with 

 the zygapophyses fore and aft, in accord with the shortness of the centra. 

 In the more posterior vertebrse they become separated on account of the 

 increasing length of the centrum. 



"The third vertebra is like the axis, except in having a keel-shaped 

 neural spine, and a short obtuse zygosphen continued from its base anteri- 

 orly. With increasing length of centrum the diapophysis becomes longer, the 

 hypophysial ridge becomes wider, and coextensive with the inferior face of 

 the centrum. It is separated by an angle from the sides in the longer verte- 

 brae; in those of intermediate length the inferior face is convex. All of them 

 retain the delicate lines and punctse of the inferior surface. The neural 

 spine on the more elongate vertebrse is a rather elevated keel with horizontal 

 superior edge. Its posterior extremity forms a wedge-like zygosphen. The 

 zygantrum is a deep V-shaped cavity, opening posteriorly and not roofed 

 over at any point, unless for a small part of its fundus. The zygapophyses 

 are well spread and have horizontal faces. Each of the columns of the dia- 

 pophysis sends a ridge forwards, which inclose a groove between them. 



"Measurements of vertebrts. 



M U 



"Length of atlas below 0.015 Length of centrum of another (No. 



Length of atlas at zygantropophyses .029 IV) 022 



Expanse of atlas at condyloid facets .034 Expanse of postzygapophyses of do. .018 



Expanse of centrum atlas behind .. . .0145 Length of centrum of No. V 022 



Depth of atlas at middle 019 Diameters centrum V anteriorly: 



Length of axis below 015 Vertical 013 



Length of axis at zygantropophyses .016 Transverse 012 



Width of zygosphen above on Expanse prezygapophyses .021 



Expanse of postzygapophyses 024 Elevation of neural spine from 



Width of centrum posteriorly 012 centrum on 



Depth of centrum posteriorly Diameters centrum No. VI: 



Length of centrum of another (No. Anteroposterior 023 



III) 018 Vertical on 



Transverse 013 



"The vertebrae of this species are very much larger than those of the 

 D. salamandroides, and the diapophyses do not originate so low down on 

 the centrum. Otherwise they are much ahke. The cranium of the Illinois 

 species is yet undetermined." 



Cope adds, in his second paper cited: 



"In the typical specimen the posterior border of the skull was not 

 preserved. The present specimen shows that it was continuous from the 

 extremity of one horn to that of the other, and regularly concave without 

 angles, and that it overhangs the occipital condyles a little. The posterior 

 parts of the horns consist of the tabular bones, and the anterior portion con- 

 sists of the supratemporals. The inferior part of the base of the horn 

 externally consists of the element which articulates with the quadrate, or 

 quadratojugal. It is distinguished from the supratemporal by a horizontal 



