THE FISHES 161 



Often this organ is altogether wanting, as in the common 

 mackerel. About ten thousand kinds of bony fishes are 

 known. The species swarm in every sea, lake, or river 

 throughout the earth, and some form or another among 

 them is familiar to every boy in the land. These fishes are 

 divided into about two hundred families, and these may be 

 arranged in fifteen to twenty orders. As these are mostly 

 distinguished by features of the skeleton, we need not name 

 them here. In Jordan and Evermann's Fishes of North and 

 Middle America, as well as in various other books, the stu- 

 dent of fishes can find the characters by which orders may 

 be distinguished. 



155. Sturgeons and garpikes (Ganoidea). While the great 

 majority of the typical fishes possess a bony skeleton, there 

 are a few quaint types the ganoid fishes, such as the stur- 

 geons (Fig. 101) and garpikes in which it is cartilaginous or 

 partly bony. In past ages these were probably the highest 

 type of fishes, and from their fossil remains we may con- 

 clude that they flourished in vast numbers ; but at present 

 they are almost extinct. In this country the ganoids are 

 represented by several species, the best known being the 

 sturgeons which inhabit the Great Lakes, the Mississippi, 

 and its tributaries; while on the East coast the common 

 sturgeon (Acipenser sturio) often leaves the sea and ascends 

 rivers. They are the largest fishes found in fresh water, 

 attaining a length of ten or twelve feet, and a weight of 

 five hundred pounds. Their food consists of small plants 

 and animals, which they suck in through their tube-like 

 mouth. The garpikes live in the larger lakes and rivers 

 throughout the East and Mississippi Valley. Their bodies, 

 from three to ten feet in length, according to the species, 

 are covered with comparatively large regularly arranged 

 square scales, and the upper jaw is elongated to form a 

 kind of beak, abundantly supplied with teeth. They are 

 carnivorous, voracious fishes, working great havoc among 

 the more defenseless food-fishes. 



