SPTNY-RAYED FISHES. 



65 



a length of eight feet and a weight of 40 lb. ; individuals of this 

 large size are dangerous to bathers. They are generally used as 

 food, but sometimes (especially in the West Indies) their flesh 

 assumes poisonous qualities, in consequence of their feeding on 

 smaller poisonous fishes, particularly certain Clupeoids. 



The Scombrida, or Mackerel family (Cases 10, 11), are pelagic [Case 10.] 

 forms, abundant in all the seas of the tropical and temperate 

 zones. They are one of the four families of fishes which are the 

 most useful to man, the others being the Gadoids, Clupeoids, and 

 Salmonoids. They are fishes of prey and are unceasingly active, 

 their power of endurance in swimming being equal to the rapidity 

 of their motions. They wander about in shoals, spawn in the open 

 sea, but periodically approach the shore, probably in the pursuit of 

 other fishes on which they feed. The type of this family is the 

 Common Mackerel (Scomber scomber). The Tunny (Thynnus 

 thynnus), abundant in the Mediterranean, and ranging to the south 

 coast of England and to Tasmania, is one of the largest fishes of 

 the Ocean A attaining to a length of 10 feet and to a weight of 

 more than 1000 pounds. The fishery of the Tunny is systemati- 

 cally carried on in the Mediterranean. To the same genus belongs 

 the Albacore (T. albacora). Specimens of both these species are 

 exhibited in a separate table-case. Other highly esteemed fishes [Case 11.] 

 of this family are the "John Dorys" (Zeus). The remarkable 

 Sucking-fishes (Echeneis) have the spinous dorsal fin modified into 



Fig. 48. 



Sucking-fish (Echeneis scutata) ; with separate view of sucking-disk. 

 (Indian Ocean.) 



