94 AMERICAN PERMIAN VERTEBRATES 



The axis has a rather long, stout, not very high spine; it has 

 feeble articulations in front for the atlantal arches. It has a rather 

 short, but stout diapophysis on each side, directed downward and 

 somewhat posteriorly, for the axial rib, which, however, has not 

 yet been recovered in natural relations. 



Of the succeeding twenty-five presacral vertebrae, the spines 

 are nearly uniform in character, save of the posterior five or six. 

 They are vertical in position, flat and thin, a little broader above, 

 with a very thin front edge and a somewhat thicker posterior one, 

 and are equal in height to about three times the vertical diameter 

 of the centra; the upper end is rather squarely truncate. With the 

 sixth presacral the spines begin to inchne a little forward, becoming 

 successively more oblique and more pointed and roimded at the 

 end. The highest spines are those between the tenth and fifteenth 

 presacrals, but the increased height is not great. The zygapophyses 

 are nowhere very broad or stout, their articular surfaces looking 

 uniformly obHquely outward and inward. The shapes and posi- 

 tions of the diapophyses are shown sufl&ciently well by the figures, 

 and need but a brief description. As seen in Plate II, Fig. i, they 

 are the largest, stoutest, and longest on the anterior vertebrae, 

 about opposite the upper end of the scapulae, from the twentieth 

 to the twenty-fourth presacral, quite in the corresponding part of 

 the column in the lizards. Anteriorly they are directed more 

 downward and backward; on the twenty-first and twenty-second 

 downward; on all the following directly outward. From the 

 twenty-first backward, they decrease gradually in length and in 

 stoutness. The last five diapophyses — that is, those of the first 

 five presacrals — have short ribs co-ossified with them, as in other 

 Permian reptiles as a rule, the head descending a httle on the body, 

 leaving a small foramen between it and the tubercle. 



The centra, unUke those of Casea, are of nearly uniform length 

 throughout, somewhat shorter and higher posteriorly; anteriorly 

 the "pinching in" of the sides produces a rather sharp keel below, 

 but posteriorly this keel is broader and more rounded. Intercentra 

 are in place, as shown in the figures, between various ones of the 

 vertebrae; they are of moderately large size, larger than in Casea. 

 Between the third and fourth, and the fourth and fifth, and less 



