CLASS PISCES 



463 



them are rudimentary and covered with a thick skin. Amblyop- 

 sis spclaus (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 calloplcrus. (From Lankester's Treatise, 



after Giinther.) 



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 ANGUILLID.E. - - The Eels. The true eels should not 

 be confused with the lamprey eels of the class CYCLOSTOMATA 



FIG. 395. The common uel. An^uilla rostrata. (From Jordan and 



Evermann.) 



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

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



