80 HIGH SCHOOL ZOOLOGY. 



CHAPTER. III. 



The Canadian Ajiphibia or Batrachia. 



1. Among the Dipnoi the genus Protopterus is the most 

 truly amphibious, as during part of the year it lives in a torpid 

 condition in the dried mud of the river-beds and is entirely 

 dependent upon its lungs for respiration. It therefore deserves 

 to be called amphibious, far more than do certain members of 

 the Class Amphibia or Batrachia, such as the common Mud- 

 puppy or Menobranch of our Lakes (Necturus maculatus) 

 (Fig. 58), which can live but a very short time out of water. It 



Fig. 58.— Canadian Lake Lizard, or Menobranch. 

 (Kectxirus mactdafus.) 



is important to compare such a fish-like Batrachian with a true 

 fish, to find out the precise structural difierences between the two. 

 The head in the Menobranch is flattened as it is in the catfish, 

 but a distinct neck separates it from the trunk, and here are 

 situated the three pairs of external gills attached to the outside 

 of the corresponding gill-arches and separated by two gill-slits. 

 It has been found that these slits correspond to those between 

 the first and second, and second and third branchial arches in 

 the fish. 



