scales. Range: Eastern and Central United
States.]

Many fishes are valuable as food and the fisheries are extensive
industries, in which large sums of money are invested.

There are four great groups of fishes:

1. The sharks and rays, with cartilaginous skeletons.

2. The ganoids of which the sturgeon and garpike are examples, with
heavy plates or scales.

3. The bony fishes--salmon, pickerel, mackerel, cod, halibut, etc.

4. The lung fishes, that live partly in air.

[Illustration: SHOVEL-NOSED STURGEON

This fish is covered with bony plates instead of scales. The roe is made
into caviar. _Range_: Upper and middle Mississippi Valley.]

There are many species of sharks. Among the more common ones in Atlantic
waters are the Smooth Dogfish which have pavement-like teeth; the Sand
Shark with catlike teeth; the Hammerhead Shark with its eyes on stalks.
The near relatives of the sharks are the Skates. The most common
example of the ganoid fish is the sturgeon, which is heavily clad with a
bony armor. Most of the fishes that we find, however, belong to the
third group, i. e., bony fishes. Among the salt-water species, the cod,
the halibut, the mackerel, and the bluefish are especially valuable as
food. Of the salt-water fishes that go up the rivers into fresh water to
breed, the salmon and the shad are widely known. Of a strictly
fresh-water fish, the sunfish and catfish are very common. Among the
game-fish are the trout, bass, pickerel, and salmon.

For those who live in cities, a convenient place to begin the study of
fishes is in the fish-market. Here we may learn to know the common
food-fishes by name, and to know many interesting things about them. If
there is a Public Aquarium or a Natural History Museum in your city, you
can use it in connection with the fish-market. Especially valuable in
Museums are the habitat groups of fishes, that is, those in which the
fishes are shown in their natural surroundings. But, best of all, the
place to study fishes, as is true of all other animals, is out-of-doors
in their native haunts. With your dip-net or hook and line, catch the
fish, and then by the aid of one of the books listed below find out what
its name is. Then, by observation of the fish see what is interesting in
its life-history. Find out where the mother-fish lays her eggs. Does
either parents guard them? Has the fish any natural weapons of defense?
If so, what are they? Does either parent care for the youn