The Pectoral girdle.
The pectoral girdle of the Crocodile is less complete than is that of most reptiles. It consists of a dorsal bone, the scapula, and a ventral bone, the coracoid, with a median unpaired element, the interclavicle; but there is no separate representative either of the clavicle or precoracoid.
The scapula (fig. 47, 1) is a large bone, flattened and expanded above where it is terminated by an unossified margin, the suprascapula, and thickened below where it meets the coracoid. The scapula forms about half the glenoid cavity (fig. 47, 4) for articulation with the humerus, and has the lower part of its anterior border drawn out into a roughened ridge.
The coracoid (fig. 47, 2) is a flattened bone, much expanded at either end; it bears on its upper posterior border a flattened surface which forms half the glenoid cavity, and is firmly united to the scapula at its dorsal end. Its ventral end meets the sternum.
The interclavicle (figs. 46, 1, and 47, 3) is a long narrow blade-shaped bone lying along the ventral side of the sternum; about a third of its length projects beyond the sternum in front.
The Anterior limb.
This is as usual divisible into three portions, the upper arm, fore-arm and manus.
The upper arm or brachium contains one bone, the humerus.
The humerus (fig. 48, A, 1) is a fairly long stout bone, considerably expanded at either end. The proximal end or head is evenly rounded and is formed by an epiphysis ossifying from a centre different from that forming the shaft. It articulates with the glenoid cavity. The shaft bears on the flexor surface, at some little distance behind the head, a prominent rounded protuberance, the deltoid ridge. The distal end or trochlea is also formed by an epiphysis and is partially divided by a groove into two convex surfaces; it articulates with the two bones of the fore-arm, the radius and ulna.
