94 TELEOSTEI: SYNENTOGNATHI. XVI. 



eighth of a mile, rarely rising more than 3 or 4 feet. Their move- 

 ments in the water are extremely rapid ; the sole source of motive 

 power is the action of the strong tail while in the water. No force 

 is acquired while the fish is in the air. On rising from the water, 

 the movements of the tail are continued until the whole body is out 

 of the water. While the tail is in motion, the pectorals seem to be 

 in a state of rapid vibration, but this is apparent only, due to the 

 resistance of the air to the motions of the animal. While the tail 

 is in the water, the ventrals are folded. When the action of the 

 tail ceases, the pectorals and ventrals are spread and held at rest. 

 They are not used as wings, but act rather as parachutes to hold 

 the body in the air. When the fish begins to fall, the tail touches 

 the water, when its motion again begins, and with it the apparent 

 motion of the pectorals. It is thus enabled to resume its flight, 

 which it finishes finally with a splash. While in the air it resem- 

 bles a large dragon-fly. The motion is very swift, at first in a 

 straight line, but later deflected into a curve. The motion has no 

 relation to the direction of the wind. When a vessel is passing 

 through a school of these fishes, they spring up before it, moving 

 in all directions, as grasshoppers in a meadow. 1 



The young of different species often have long fleshy barbels at 

 tip of the lower jaw. These are lost with age. They were formerly 

 placed in a separate "genus," Cypselurus Swainson. (CU>KOITOS, 

 sleeping outside ; an old name of some fish imagined to sleep on 

 the beach at night.) 



a. Anal long, its base nearly equal to that of D., its first ray opposite first of 



D.; anal rays 11 or 12; dorsal rays 11 or 12. (Exoccetus.) 

 b. Second ray of P. simple, as well as the first; 4th and 5th rays longest; 



V. largely black. 

 c. Second ray of P. scarcely longer than first. 



228. R exsiliens Miiller (1776). V. 2 in body, reaching C. ; 

 P. l; eye large. Head 4 ; depth 5. Scales 48. L. 10. P. 

 and V. marbled with black and white ; D. with black spot anteri- 

 orly ; A. white ; a dark blotch at base C. Open sea, occasional N. 

 (E. exiliens Gmelin, 1788.) (Lat., leaping out.) (Eu.) 



cc. Second ray of P. nearly half longer than first. 



229. E. rondeletii Cuv. & Val. V. 3 in body, reaching last 

 A.; P. 1| in body; eye moderate. Head 4^; depth 5. Scales 50. 

 Ventrals chiefly black ; P. dusky ; no black on D. or A. Open sea, 

 frequently N. (Eu.~) (For Guillaume Rondelet, one of the fathers 

 of ichthyology.) 



bb. Second ray of P. divided; 3d or 4th longest 



1 Observations on the flight of these fishes have been made under very favorable 

 conditions by Prof. C. H. Gilbert, and the writer. Several species have been thus 

 observed, especially the largest of the group, E. californicus Cooper. 



