170 



Descriptive Zoology. 



spines above the base of the tail, and are called " thorn- 

 backs " and " sting rays." Perhaps the largest of them is 

 the "devilfish," sometimes attaining a width of eighteen 

 feet and a weight of several tons. 



Some of the rays have a complicated electric apparatus, 



FIG. 105. COMMON SKATE (RAY). 



Jaws and teeth (above); mouth and gill slits (below). 

 From Packard's Zoology. 



with which they can give a strong shock to an animal with 

 which they come in contact. This serves both as a means 

 of defense and for securing prey. The one electric ray 

 found on the Atlantic coast has the scientific name Torpedo 

 and the common names " crampfish " and "numbfish." 



THE BONY FISHES. 



The great majority of fishes differ from the sharks and 

 rays as follows : 



i. The skeleton is bony instead of cartilaginous. 



