56 AMERICAN PERMIAN VERTEBRATES 



with the diapophysis, below which it is broadly dilated antero- 

 posteriorly, fitting closely the whole, or nearly the whole, of the 

 inner side of the upper, dilated part of the ilium, from the extreme 

 posterior angle forward, leaving no space whatever for the attach- 

 ment of a second rib, however small. Five caudal ribs are in place 

 on the right side, loosely attached to the ends of the diapophyses. 

 The first of these, on the first caudal vertebra, is separated from 

 the sacral rib and is slender like the following ones; its distal end, 

 as preserved, is pointed, and the rib is shorter than the next fol- 

 lowing one. I cannot be sure but that the end is the result of 

 fracture, the more so as a part of a rib lies transversely below it. 

 In the figure I have restored the rib, with lines, to the form of the 

 following ones, but I am inclined to believe that the whole rib is 

 present, and that the one below it belongs with the opposite side. 

 However, even if short, it could have had no part in the support 

 of the ilium, nor did it even touch it, proving conclusively, for the 

 first time, I believe, the presence of but a single sacral vertebra in 

 a reptile. All of the caudal ribs preserved are slightly dilated and 

 flattened at their distal extremity. They do not decrease much 

 in length, from which it would appear that the tail in life was 

 ribbed for a considerable part of its extent. 



Pectoral girdle and extremity. — The pectoral girdle has suffered 

 little distortion or displacement; on the right side it is thrust 

 forward a little, or, on the opposite side, backward. The expanded 

 parts of the clavicles, in close articulation with the interclavicle, 

 lie under the occipital region, close up to the angle of the jaws. 

 The ascending more slender part of the clavicles is applied rather 

 closely to the quadrate, permitting very little lateral movement 

 of the skull on the vertebral column. The larger part of the inter- 

 clavicle is hidden above the clavicles, leaving only a diamond- 

 shaped surface exposed in the middle behind. Its stem is stout 

 and rather broad, oval in cross-section, tapering slightly to about 

 its middle, and then gently expanded to the extremity, which 

 reached as far as the eighth or the beginning of the ninth vertebra, 

 and far back of the coracoid. The clavicles are much dilated on 

 the ventral side, with a convex thin border in front to near the 

 angle of the jaws, where it turns sharply upward, backward, and a 



