152 FIRST LESSONS IN ZOOLOGY. 



fishes have in places survived by reason of their vigor, fe- 

 rocity, big jaws and teeth, as well as their thick, close-set, 

 enamelled scales. 



While one branch of the ichthyic tree of life ended in the 

 garpike, a twig from this branch is represented by the mud- 

 fish. 



The mud-fish of Western and Southern waters (Amia 

 calva) is a connecting link between the Ganoids and com- 

 mon or bony fishes. It bears a general resemblance to and 

 is about the size of a small bass. Its tail is less uneven or 

 " heterocercal " than that of the garpike, and thus it comes 

 nearer to the bony fishes. Its spinal column and skull are 

 also bony, and it indeed differs but in details from the 

 bony fishes. 



