CLASS PISCES 469 



Atlantic, swimming about in enormous schools. It feeds on 

 small aquatic animals, such as CRUSTACEA, and furnishes food 

 for other fishes. It is also a valuable food-fish for man. The 

 Spanish mackerel, S comber omorus maculatus, is also a common 

 food- fish of the North Atlantic. The tuna, Thunnus thynnus, 

 is called the tunny or horse-mackerel on our eastern coast, but 

 is the tuna of California. They are eagerly sought with hook 



FIG. 402. The mackerel, Scomber scombrus. (From Jordan and Evermann.) 



and line, and many have been landed by this means that weighed 

 over one hundred pounds. 



Family XIPHIID^E. The Swordfishes. The single species, 

 Xiphias gladius, belonging to this family is widely distributed 

 in salt waters. It reaches a maximum weight of about six hun- 

 dred pounds, and its prolonged upper jaw makes it a formidable 

 foe. Sometimes fishing boats are pierced and sunk by the 

 sword of large individuals. The food of the swordfish consists 

 of squids, mackerel, menhaden, and other fish, and it in turn is 

 a valuable article of food for man. 



Family PLEURONECTID^E. The Flounders. These are flat- 

 fishes known as flounders, halibuts, soles, plaice, and turbots. 

 They are flattened from side to side, and thus adapted for life 

 on the sea bottom. Frequently they are colored on the upper 

 surface so as to resemble the sand or other material surrounding 

 them. The young flatfish resembles an ordinary fish when it 

 hatches, but it soon begins to broaden laterally and swim on its 

 side, while the eye on the lower side moves around to the upper 



