[Illustration FIG. 46. STERNUM AND ASSOCIATED MEMBRANE BONES OF A CROCODILE (_C. palustris_) × 1/3. (Brit. Mus.) The last pair of abdominal ribs which are united with the epipubes by a plate of cartilage have been omitted. 1. interclavicle. 2. sternum. 3. sternal rib. 4. abdominal splint rib. 5. xiphisternal horn.] 2. THE APPENDICULAR SKELETON. This includes the skeleton of the two pairs of limbs and their respective girdles. [Illustration: FIG. 47. LEFT HALF OF THE PECTORAL GIRDLE OF AN ALLIGATOR (_Caiman latirostris_) × 2/3. (Brit. Mus.) 1. scapula. 2. coracoid. 3. interclavicle. 4. glenoid cavity.] 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. [Illustration FIG. 48. A, RIGHT ANTERIOR, AND B, RIGHT POSTERIOR LIMB OF A YOUNG ALLIGATOR (_Caiman latirostris_). (Brit. Mus.) A × 1/2. B × about 1/3.]