ANOURA. 



309 



Fig. 161. 



Fig. 162. 



lungs are two, equal, and the F{S - l6 - 

 heart is composed of only one 

 auricle and one ventricle. In 

 the higher forms the vertebrae 

 are convex at one end and 

 concave at the other ; but in 

 some cases the vertebrae are 

 concave at both ends. 



Batrachians comprise three 

 orders, Anoura or Tailless 

 Batrachians, Urodela or Tailed 

 Batrachians, and Apoda or Cas- 

 cilians. Besides these, there 

 is a group of extinct batrachi- 

 ans called Labyrinthodonts, 

 from the peculiar internal 

 structure of their teeth. They 

 have scales, and are first found 

 in the Carboniferous, and cul- change 

 minate and end in the Trias- 

 sic rocks. Some of the species were very large. 



Fig. 164. 



Fig. 165. 



the form of a Batrachian 

 the Frog from the time of hatching. 



SUB-SECTION I. 



THE ORDER OF ANOURA, OR TAILLESS BATRACHIANS. 



THE Order of Anoura comprises batrachians which 

 have the body short, thick, and covered with a skin which 

 does not adhere to the muscles, but covers them loosely 

 like a sack. The tongue is long, and fixed to the front 

 of the jaw, and its tip turned backwards in the mouth, 

 whence it can be darted forth with almost lightning 

 swiftness ; and it is in this way that these animals secure 

 the living insects which constitute their food. The 

 young are tadpoles (Figs. 160-163), which have a large 

 head, short, thick body, and a long compressed tail, and 



