CLASS PISCES 



463 



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

 sis spelceus (Fig. 393) is common in the river Styx of the Mam- 

 moth Cave. 



Family EXOCCETID.E. The Flying-fishes (Fig. 394). There 

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



FIG. 394. A flying fish, Exoccetus callopterus. 

 after Giinther.) 



(From Lankester's Treatise, 



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, but simply sustain the body in the 

 air. 



Family ANGUILLHXE. The Eels. The true eels should not' 

 be confused with the lamprey eels of the class CYCLOSTOMATA 



FIG. 395. The common eel, Anguilla rostrata. 

 Evermann.) 



(From Jordan and 



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

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



