FISHES. 331 



eye of that side migrates to the upper surface, twisting the 

 bones of the skull in its progress. Henceforth the fish 

 lives constantly in this peculiar position, the side of the 

 body turned downward being white, the other colored. 

 The halibut, occurring in all northern seas, are among 

 the largest fishes, occasionally weighing 350 to 400 pounds. 



ORDER III. ACANTHOPTERI (Spiny-firmed Fishes). 



In this, the largest order of bony fishes, the gills are 

 comb-like, the jaw-bones are movable (p. 24), and the 

 dorsal, anal, and ventral fins have spiny rays in front. In 

 some there is a swim-bladder, but it is without connection 

 with the gullet. Among the strange modifications in the 

 group are the suck-fish or Remoras (fig. 131), in which 





FIG. 131. Remora (Remoropsis brachyptera}. After Goode. The sucker is 



shown on the top of the head. 



part of the dorsal fin is modified into a sucker, by which 

 they attach themselves to other fishes or floating objects, 

 and are thus carried about. 



In the swordfishes the bones of the upper jaw are modi- 

 fied into a long, stiff sword terminating the snout, and 

 used as a weapon of offence and defence. The largest 

 species reaches a length of fifteen feet. In other points 

 of structure the swordfish are much like the mackerels, 

 (fig. 132), pompanos, and bluefish, so well known as food- 

 fish. Of these the largest is the tunny or horse-mack- 

 erel, which sometimes weighs 1500 pounds. 



