72 NEW REPTILES AND STEGOCEPHALIANS FROM 



process of the crest is intermediate in length between that of Nos. 7322 and 7244, reaching 

 about halfway to the articulation with the pubis. This process is much thinner on the 

 upper edge even than No. 7322, as the outer side is beveled by a rough surface. The 

 posterior process is relatively much longer than in either of the others and extends 

 backward with much the same slant as in No. 7322. The posterior extremity is thickened 

 by the inward curvature of the lower edge, the face thus formed looking almost directly 

 downward. The cotylus is exceptionally deep, as there is a strong buttress developed 

 near its anterior edge which maintains its width to the upper edge of the bone. The 

 upper edge of the cotylus is extended forward on the anterior portion of the bone, forming 

 a sharp ridge and giving the whole region, and the articular face for the pubis, a triangular 

 section. The articular faces for the ischium and the pubis are exceptionally heavy. 

 On the inner side there are no deep cavities for the articulation of the distal ends of the 

 sacral ribs. The upper portion of the blade is smooth and is free above the sacrum for 

 some distance; this surface is only gently concave. The upper edge of the ilium is 

 thickened at the anterior and posterior edges, but the median portion is quite thin and 

 sharp. This is decidedly different from the two other forms described, where the upper 

 edge is thick and heavy throughout its length, the median part being nearly as thick as 

 either of the ends. 



No. 7266, discovered near the head of Holmes Creek, in Crosby County, Texas, 

 consists of the two ilia and the sacral vertebrae complete, except for the neural spines. 

 The specimen has been slightly crushed from above downward, but not enough to materi- 

 ally distort the specimen. The ilia are similar in form to No. 7333, but nearly twice 

 as large; they probably belong to an animal of the same species, but of larger size. The 

 anterior process of the blade of the ilium (fig. 27 e) is relatively slender, reaching a little 

 more than halfway to the articulation with the pubis; its extremity is very slightly 

 down-curved. The posterior process is long, and the lower edge extends backward, 

 almost directly from the articulation with the ischium, at a gentle angle. The cotylus 

 is deep, especially near the anterior end, where there is a strong buttress reaching down 

 from the upper edge of the bone to the upper edge of the cotylus. The articular edges 

 for the ischium and pubis meet in a large angle. The upper edge of the blade is relatively 

 thin, with slight thickenings at the anterior and posterior ends. The articular portions 

 of these edges outside of the cotylus are very heavy. The slight depression of the 

 pelvis has thrown the lower edges of the ilia inward and the upper edges outward, slightly, 

 BO there is an apparent flattening of the upper surface. The blade of the ilium on each 

 side rises free from the upper surfaces of the sacral vertebrae, and there is a decided 

 concave area on each bone on the inner upper side. The articulation of the distal ends 

 of the sacral ribs is close and firm, the anterior one being received in deep rugose pits 

 and the posterior one articulating along the length of a rather heavy ridge (fig. 28 a; 

 plate 12, figs, a and b). 



The sacrum is formed of two heavy vertebrae; the neural spines have been destroyed 

 and the neural arches are pressed downward, almost closing the neural canal, but they 

 were not high even in the undistorted specimen. The t wo vertebrae were not anchylosed, 

 even in this evidently adult specimen, and the zygapophyses between the two sacral 

 vertebrae are still well formed and distinct, though somewhat injured. The sacral ribs are 

 very wide and strong, giving a powerful attachment of the pelvis to the vertebral column. 

 The ribs originate high upon the sides of the neural arch, almost at the level of the zyga- 

 pophyBee; there is no indication of sutures at the proximal end.-. The anterior ribs 

 originate along the full length of the side of the vertebrae, the anterior edges being as far 

 forward M the anterior ext remit v of the prezygapophysis, and the posterior edges originat- 

 ing relatively as far back. This rib is very heavy at its proximal end and becomes more 

 so as it extends outward in a fan-shape; the distal end is at least 3 centimeters thick 



