284 ELEMENTARY ZOOLOGY 



genus (Anguilla] or true eel which ascends the rivers is 

 exceedingly abundant and widely distributed. Most eels 

 are extremely voracious, but some of them have mouths 

 that would barely admit a pin-head. The codfish (Gadus 

 callarias) is a creature of little beauty but of great useful- 

 ness, swarming in all arctic and subarctic seas. The 



FIG. 116. The winter flounder, Pseudopleuronectes americanus. 

 (After Goode. ) 



herring (Clupea Jiarengiis]^ soft and weak in body, are 

 more numerous in individuals than any other fishes. The 

 flounders (fig. 116) of many kinds lie flat on the sea- 

 bottom. They have the head so twisted that the two 

 eyes occur both together on the uppermost side. The 

 members of the great mackerel tribe swim in the open 

 sea, often in great schools. Largest and swiftest of these 

 is the sword-fish (Xipliias gladius), in which the whole 

 upper jaw is grown together to form a long bony sword, 

 a weapon of offence that can pierce the wooden bottom 

 of a boat. 



Many of the ocean fishes are of strange form and ap- 

 pearance. The sea-horses (Hippocampus sp.) (fig. 117) 

 are odd fishes covered with a bony shell and with the 

 head having the physiognomy of that of a horse. They 

 are little fishes rarely a foot long, and cling by their 



