SELACHII. 23 



the fact that the pectoral fins are enclosed in it, the whole 

 making a disk, rounded or four-sided in outline. Most of 

 them are bottom feeders, living upon shell-fish, and hence 

 have flattened pavement- teeth. The torpedoes are remark- 

 able for their electrical powers. In them certain muscles 

 on the sides of the head are metamorphosed into an elec- 

 trical battery, the discharge of which is under control of 

 the will. The current is strong enough to kill small 

 animals which come into contact with the creature. The 

 largest of the skates are the huge tropical devil-fish, which 

 reach a length of twelve or more feet and a weight of 1200 

 Ibs. 



