280 



ZOOLOGY 



APPENDIX TO CHAPTER XVIII 



KEY TO THE FOUR ORDERS OF REPTILES 



i. Trunk enclosed in a case composed of a dorsal and 

 a ventral shield (carapace and plastron) ; jaws 

 without teeth ....... 



.j. Without encasing shields ; teeth on jaws. 



b\. Teeth in special cups or alveoli ; 4 legs ; 



cloacal opening a longitudinal slit 

 f>-2. Teeth not in special alveoli ; cloacal opening a 



transverse slit, 

 fi. Shoulder girdle and sternum present ; 



eyelids usually present 



c-j. Shoulder girdle and sternum absent ; eye- 

 lids absent ; no feet .... 



Chelonia 



Crocodilina 



Sauria 



