REPTILIA.
REPTILES may be briefly defined as cold-blooded Vertebrates breathing by lungs throughout their existence, and having the body covered with scales or scutes. A basioccipital bone is present in the skull, which articulates with the vertebral column by a single condyle.
The class Reptilia is divided into a considerable number of Orders, which are, however, mostly extinct. Recent Reptiles belong to four Orders, viz. :
I. EMYDOSAURIA, Crocodiles.
II. CHELONIA, Tortoises and Turtles.
III. SQUAMATA, Lizards and Snakes.
IV. RHYNCHOCEPHALIA, a primitive type, probably ancestral to the three others, and of which a single existing representative is known, the Tuatera of New Zealand.
Order I. EMYDOSAURIA.
Quadrate bone immovably united to cranial arches ; two horizontal bony temporal arches. Cervical and dorsal ribs mostly two-headed, the middle dorsals articulating with the transverse processes of the neural arch. Sternum and interclavicle present ; seven or eight transverse series of " abdominal ribs," not connected with the vertebral ribs, each series composed of four ossicles, and forming an angle directed forwards. Teeth present in the jaws, implanted in alveoli. Ventricle of the heart divided by a complete septum. Pectoral and abdominal cavities separated from each other by a muscular diaphragm. Anal opening longitudinal. Copulatory organ present, single.
