62 GUIDE TO THE AUSTRALIAN MUSEUM. 



YIII. 



t 



EEPTILIA AND BATRACHIA. 



The reptiles and the BATRACHIANS have so manjr 

 characteristics in common tliat it is convenient to study them 

 side by side, althougli the modern system of classification does not 

 group them together. , 



REPTILES include snakes, lizards, tortoises, turtles, croco- 

 diles, and alligators ; they are air-breathing animals, with large 

 lungs and cold blood. 



BATRACniANS differ from reptiles in having the skull 

 united to the backbone by two joints or condyles, while reptiles 

 have only one, and by having no scales. Most of the Batrachians 

 have four limbs like the higher animals. They lay eggs and have 

 cold blood. The Batrachians consist of animals which during the 

 early stage of their development undergo a complete metamor- 

 phosis, living in water and breathing like fishes by means of 

 gills, which in the adult state disappear and are replaced by 

 lungs, while at the same time the tail, in the greater number of 

 forms, is shed, and four limbs are developed. 



Reptiles and Batrachians are divided into orders as on page 16. 



REPTILIA— Order I.— OHELONIA.— The Tortoises 

 and Turtles which form this order are the only reptiles which have 

 not distinctly elongated bodies. They are protected by a hard 

 bony outer skeleton, technically known as the exo-skeleton, 

 formed of horny plates. The vertebrae are united, making the 

 backbone practically one straight bone. They have no teeth, 

 these being replaced by a horny beak. The head, limbs, and 

 tail protrude from openings in the carapace, and can, in most 

 si)ecies be withdrawn at will. In the Central Hall, upper floor, 

 are specimens shewing the formation of the skeleton, and the 

 following mounted examples : — 



The Murray River, or Long-necked Tortoises {Chdodina 



longicollis and C. ohlonga.) 



