HERRING 247

the wrasses are herbivorous, while some live on corals
and echinoderms. They are nearly all highly
coloured, the most brilliant being, perhaps, the parrot
wrasses of the Indian Ocean. ;

In the next assemblage, the Anacanthinz, without
spines in the anal, pelvic, and dorsal fins, are the cods
and the turbots. In the cod group (Gadozdez) are
four families, the most important of which are the
Gadide, which include not only the cod and the
haddock, but the whiting, the pollack, the hake, and
the ling. Thesand-eels used for bait are also gadoids,
as also are the macrurid fishes, found, some of them,
three miles down in the ocean, and represented by
about forty species distributed all over the globe.
To the Pleuronectede belong most of the better-class
flat fishes used as food—those which have the head
twisted so as to bring both eyes on one side, like the
turbot, the sole, the brill, the plaice, the flounder, and
the halibut, which is the largest of all.

In the next category—for there are over 12,000
species of fishes, and we must be brief—the central
group is that of the herring brigade. There are
nearly thirty other groups, all distinguished by
having the fin-rays articulated, the ventral fins, when
present, being without spines, and the air-bladder, if
present, having a pneumatic duct. The cat-fishes
have no scales ; their skins are either naked or pro-
tected by bony scutes. With the exception of the
sturgeon, they are the largest of European fresh-water
fish. In tropical Africa there is an electric cat-fish
(Malapterus) ; in tropical America there is one (Cal/-
achthys) which has huge overlapping shields on its