B. The Endoskeleton

I. The Vertebral Column.

Fig. 16.—Skeleton of Crocodile. D, dorsal region; L, lumbar region; Sa, sacral region; Ri, ribs; Sc, scapula; H, humerus: R, radius; U, ulna; Sta, sternum abdominale: Fe, femur; T, tibia; J, ischium; C, caudal vertebræ. (From Claus & Sedgwick.)

The vertebral column consists of about sixty-five vertebræ, which may be separated into the usual regions; there are nine cervical, ten dorsal, five lumbar, two sacral, and about thirty-nine caudal. It is likely that the number of caudals may be subject to frequent variation; one complete skeleton had sixty-five vertebræ in all, another had sixty-eight. A complete skeleton of the crocodile (species not known) had sixty vertebræ. A thirteen-foot skeleton at Western Reserve University had only sixty-one vertebræ, but some of the caudals were evidently missing. Two skeletons of C. porosus in the museum at Singapore had sixty and sixty-three vertebræ respectively. A skeleton of Tomistoma schlegeli in the same museum had sixty vertebræ.

The Cervical Vertebræ.

Since all of the cervical vertebræ bear ribs, we shall assume the distinction between them and the dorsal vertebræ to be that the ribs of the latter meet the sternum, while those of the former do not reach to the sternum. Assuming this distinction, there are, as was said above, nine cervical vertebræ.

Fig. 17. First Four Cervical Vertebræ of a Crocodile (C. vulgaris). (From Reynolds, partly after Von Zittel.)