THE VERTEBRATES 421 



abundant. Some of the lampreys attain a length of over 

 three feet. They are excellent as food fishes, especially in 

 Europe. 



(2) The fishes with skeletons of cartilage include the sharks, 

 dog-fishes, and rays. They are found in sea-water. Some 

 sharks have been caught at depths below 500 fathoms. 

 Their flesh is not esteemed as food. 



Dog-fishes are shark-like. Saw-fishes have shark-like 

 bodies with a saw-like structure on the snout. Sword- 

 fishes are similar, but with a sword in place of the saw. 

 Sting-rays have a caudal spine, which may cause severe 

 wounds. Torpedoes have electric organs, some of which 

 can disable a man. Skates are harmless. 



Specimens of the fishes named above should be viewed at 

 some museum ; or, at least, examine pictures in encyclopedias 

 and zoological books. 



(3) Most important commercially and most numerous in 

 species and individuals are the bony fishes. The sturgeons 

 and gar-pikes are the lowest examples. They have large 

 plate-like scales which form a strong armor over the skin. 

 The sturgeons are large fishes ; and their flesh is valuable as 

 food, and their ovaries are made into caviare. They live 

 in seas and rivers. The gar-pikes of North American rivers 

 are of no value as food. 



The vast majority of existing fishes in seas and fresh water 

 are of the type represented by such common fishes as cod, 

 perch, minnow, gold-fish, whitefish, bass, pickerel, salmon, 

 trout, carp, mackerel, and halibut. 



The skin of many of the bony fishes is beautifully colored, 

 and some can change their color quickly. Scales are absent 

 in most eels and cat-fishes. Many bony fishes are curiously 

 modified, as the sea-horse, flying-fishes, sword-fishes, sea- 

 robin, toad-fish, blind-fishes, etc. For accounts of these, 

 see encyclopedias, or Jordan and Evermann's "American 

 Fishes." 



