The axial skeleton includes the vertebral column, the ribs, and the skull.
A. The Vertebral column and Ribs.
The number of vertebrae in the Green Turtle is thirty-eight, not a great number as compared with that in many reptiles, and of these eighteen are caudal.
The vertebral column is divisible into four regions only—cervical, thoracic, sacral, and caudal.
The Cervical vertebrae.
These are eight in number, and are chiefly remarkable for the great variety of articulating surfaces which their centra present, and for their mobility upon one another.
The first or atlas vertebra differs much from all the others and consists of the following parts:—
a. the neural arch, formed of two separate ossifications united in the mid-dorsal line;
b. the inferior arch;
c. the centrum, which is detached from the rest and forms the odontoid process of the second vertebra.