Introduction 



as in the case of Snakes and Lizards; like the Turtles, possess a 

 bony box-like shell; or like the Crocodiles and many extinct forms, 

 have bony plates in the skin. Unlike the Batrachians, the Rep- 

 tiles breathe throughout their lives by means of lungs — in cer- 

 tain cases helped by the walls of the pharynx — and when adapted 

 in other ways for water life, remain divers merely. 



Batrachian eggs are laid in the water and hatch into so-called 

 tadpoles, different from the adults in appearance and thoroughly 

 adapted for water life. The eggs of Reptiles are laid on land, and 

 they hatch into perfected diminutive Reptiles fully adapted for 

 land life.* 



II. Two Orders of Living North American Batrachians — Urodela 

 and Salientia 



The living North American Batrachians differ enough to al- 

 low classification into two distinct Orders, the Urodela and the 

 Salientia. The Urodela are the Tailed Batrachians, or Salaman- 

 ders, with various popular names, such as Mud Puppies or Water 

 Dogs, Tritons, Newts, and Efts. The Salientia are the Tailless 

 Batrachians, i. e. the Toads, Tree Frogs, Frogs, and all Batrachians 

 that have the frog-like form. 



There can never be any confusion in identifying a Batra- 

 chian as a member of one or the other of these two Orders. The 

 Urodele is always tailed, has an elongated body and legs of nearly 

 equal size; while any member of the Salientia has a relatively 

 short stout body without a tail and with the long hind legs de- 

 veloped for jumping and swimming.^ 



The members of the Order Urodela vary considerably in 

 their habits and life histories. Like all the Batrachians, they 

 usually pass through a larval aquatic existence, after which they 



1 The technical differences in the skeletons are as follows: 



The vertebrae of Reptilia are gastrocentrous, those of Batrachia never so; Batrachian skeleton 

 never has sternal ribs and a true sternum; Batrachia have two occipital condyles for the articulatioa 

 of the skuU with the vertebral column, Reptilia have only one. 



* Technical difierences of the skeletons are as follows: 



The acentrous and opisthocoelous or amphicoelous vertebra of the Urodela are many in number. 

 The trunk venebra; carry ribs or vestiges of them. The shoulder -girdle is simple, mainly cartilagi- 

 nous, and not a complete circle — the precoracoids not meeting in the midventral line. The pehnc 

 girdle is weak, with the ilia placed at right angles to the axis. 



The Salientia have few vertebrae, which are usually notocentrous and procoelous; the last bone 

 of the vertebral column (Fig. 6) is a long solid coccyx to give suppKsrt to muscles for leaping. This 

 coccyx consists of several vertebral segments coalesced. The peine girdle is large and strong; ribs 

 are absent except in Discoglossidz. The shoulder -girdle is a complete circle overlapping or fusing 

 in front. (See Fig. s) 



2 



