160 



MARINE PRODUCTS OF COMMERCE 



fresh-water gars. The salt-water gars, too, have greatly produced jaws (Fig. 10- 

 16), but they are weak. The halfbeaks, as the name implies, have only one jaw, 

 the lower one, greatly produced. This is an instance of a superior mouth which 

 is nevertheless nearly horizontal. Swordfish, marlins, and sailfish, on the other 

 hand, have a produced upper jaw and, therefore, an inferior mouth, which 

 is, as in the halfbeaks, nearly horizontal (Fig. 10-17). 



Inferior mouths, though less common than terminal mouths, may be found 

 among the numerous species of sharks, skates and rays (Fig. 10-18), and 



{Courtesy U. S. Fish and IVildlife Service) 



Fig. 10-16. Needlefish (Tylosurus marinus) or salt water garfish. 



sturgeons (Fig. 10-19) . Superior mouths are not uncommon either, though perhaps 

 less common than the inferior. They occur among the anglers, which have ex- 

 cessively large mouths in proportion to their size. In fact, the common angler, 

 Lophius piscatorius, of the Atlantic Coast of the United States, is commonly known 

 as "allmouth" because of its excessively large oral opening. Superior mouths occur 

 even among the large family of croakers, sea trout, and drumlish (Sciaenidae) , 

 as in the genera, Larimus and Nebris, and also in stargazers, frogfish, etc. 



(,Courtesy U. S. Fish and Wildlife Service) 



Fig. 10-17. Swordfish {Xiphias gladius). 



It is interesting that in many species the position of the mouth changes during 

 growth. Commonly, it is vertical, or at least strongly obhque, in the larvae and 

 becomes terminal or even somewhat inferior in the adult. Such a change occurs 

 in the Spanish mackerel, Scomberomorus maculatus, spot, Leiostomus xanthurus, 

 croaker, Micropogon undulatus, hake, Urophycis chuss, etc. 



Teeth. Teeth, like the other structures of the fish, di£Fer greatly among the 

 various groups, or even within a family. While virtually all young fish, that is 

 postlarvae and young adults, have teeth, they are sometimes lost later in life. The 



