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. EMYDOSAUEIA, Crocodiles. 

 II. CHELONIA, Tortoises and Turtles. 



III. SQTJAMATA, Lizards and Snakes. 



IV. RHYNCHOCEPHALIA, a primitive type, probably ances- 

 tral 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 hori- 

 zontal 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. 



