more elongated, in bipedal forms slender. The scapula of the Cotylosauria (Figs. 95, 96, b, c) is relatively short and broad; that of the Theromorpha (Figs. 98, 106) more elongated, but never narrow; that of the therapsid reptiles (Fig. 107) relatively narrow, slender in the Dromasauria. The scapula of the Sauropoda (Fig. 113 d) is relatively long, that of the Predentata (Fig. 113 c) is much more slender, but it is most slender and bird-like of all in the Theropoda (Fig. 113 a, b). The scapula of the Pterosauria (Fig. 109) is always elongated, very slender and bird-like in some of the earlier forms, but stouter and firmly fused with the coracoid in the latest. In the most specialized of all pterodactyls (Pteranodon, Ornithocheirus) its enlarged distal extremity articulates with the fused spines of the dorsal vertebrae, the only known examples among vertebrates of the articular union of the pectoral girdle with the spinal column.
In the early reptiles the scapula was more nearly erect, or with a slight inclination backward. In the Crocodilia, Pterosauria, and bipedal reptiles, as also birds especially, it is very obliquely placed, the upper end turned backward over the ribs.
The Pelvic or Hip Girdle
(Figs, 114–127)
The pelvic girdle or pelvis, in reptiles, as in other air-breathing vertebrates, is composed of three bones on each side, more or less firmly coössified in the adult, and collectively known as the innominate; the girdle is completed by the sacrum on the dorsal side with which the pelvis is never closely united in reptiles, not even in the Pterosauria. The upper or dorsal bone of the three, that to which the sacral ribs or transverse process of the lumbar vertebra are attached, is the ilium; the one on the lower or ventral side in front is the pubis; that on the ventral side behind is the ischium. On the outer side, where the three bones meet, there is a cup-like depression, sometimes a hole, the acetabulum, for the articulation of the thigh bone. In only two groups of reptiles, the Crocodilia and Plesiosauria, is the pubis excluded from union with the ilium. In the snakes and snake-like lizards there are at most only vestiges of the pelvic bones.
The pelvis of the terrestrial temnospondylous amphibians (Fig. 114 a) is almost indistinguishable from that of the contemporary
