HOLOCEPHALI 



207 



the pectoral fins being much expanded. The skin is roughened 

 by spines or prickles. Rays most generally live on the bottom of 

 the sea, feeding upon fishes, 

 mollusks, crabs, and other bot- 

 tom-frequenting animals. 



To the order Sela'chii belong 

 the skates (Fig. 166), sting-rays, 

 and torpedoes or electric-rays. 

 The saw-fish ray also belongs 

 to this order. Its formidable, 

 sharp-toothed snout, several 

 feet in length, makes it a 

 dreaded enemy. It disables 

 its prey by dashing into a 

 school of fishes, striking right 

 and left. Then it eats its dis- 

 abled prey at leisure. 



SUB-CLASS II. HOLOCEPH'ALI 



This group is represented 

 on our Atlantic coast by the 

 Chimce'ra monstro'sa (Fig. 167). 

 The Holoceph'ali were formerly abundant, but are now repre- 

 sented by only a few genera. The skeleton is cartilaginous and 

 the skin is smooth. These are very peculiar looking fishes, as a 

 glance at Fig. 167 will show. The nostrils and mouth are ven- 



Fig. 166.- 



Common skate {Ra'ia 

 erinacea.) 



Fig. 167. — Chwioe'ra monstro'sa. (Claus.) 



tral. In general they resemble the sharks in their compressed 

 form, but differ from them by the large head and small mouth. 

 "Fossil remains are found from the lower Jurassic rocks upward." 



