CLASS PISCES 463 



them are rudimentary and covered with a thick skin. Ambly op- 

 sis s pel ceus (Fig. 393) is common in the river Styx of the Mam- 

 moth Cave. 



Family Exoccetid^:. — The Flying-fishes (Fig. 394). There 

 are about sixty- five species in this family, inhabiting warm 



Fig. 304. — A flying fish, Exocwtus callopterus. (From Lankester's Treatise, 



after Gunther.) 



seas. Some of them are able to leave the water, and, rising in the 

 air a few feet, " fly " a distance of from a few rods to more than 

 an eighth of a mile. It seems probable that the pectoral fins 

 do not force the fish forward, byt simply sustain the body in the 

 air. 



Family Angtjillid^e. — The Eels. The true eels should not 

 be confused with the lamprey eels of the class Cyclostomata 



Fig. 395. — The common eel, Anguilla rostrata. (From Jordan and 



Evermann.) 



(p. 414). The single species of eel, Anguilla rostrata (Fig. 395), 

 in North America occurs in the streams of the Atlantic coast. 



