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 (Actpenser 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. 
