AN INTRODUCTION TO THE VERTEBRATES 235 



i IG. 138. Types of vertebrates. 



A, a cyclostome (eel) ; B, a fish ; C, an amphibian (frog) ; D, an am- 

 phibian (salamander) ; E, a reptile (lizard) ; F, a reptile (turtle) ; G, a bird ; 

 H, a mammal (armadillo). (From various authors.) 



