PISCES. 231 
nave been accumulated in their stomachs, and which it is considered worth 
the trouble to extract. Their extreme voracity causes them to devour 
whatever comes in their way, and as the animals may be several feet in 
length, with a breadth of one third the length, the short, wide stomach and 
cesophagus readily permit a great accumulation of contents. They retain 
life for a long time after being removed from the water. A curious feature 
in Lophius consists in the possession of two long-jointed filaments on the 
head, possessing great freedom of motion in every direction, and composed 
of bone covered by skin, which at the end is dilated into a flattened 
appendage. The fish conceals itself in a dense muddiness produced by 
the action of its pectoral fins, and elevates these long filaments above its 
place of concealment, thus attracting the surrounding fishes to the glit- 
tering bait. To this habit it owes its name of fishing-frog. It also exhibits 
a peculiar structure of the teeth, which are articulated in such a manner as 
to permit them to be pressed back towards the throat, but maintaining an 
erect position when they are moved in any other direction. Thus a fish, on 
being seized and swallowed, readily passes over these jointed teeth, which 
become depressed for the purpose; but any attempt to return is prevented 
by the now erect fangs. A genus Malthea is still more repulsive in 
appearance than Lophius, various parts of the body being provided with 
fleshy filaments. The mouth is small and inferior. There are three 
known American species, some of which possess the power of executing 
considerable leaps, when left by the tide on the shore. The genus Ba- 
trachus, with somewhat the shape of Lophius, although much smaller and 
more elongated, is without filaments, except short ones on the edges of the 
lips. The first dorsal is small, the second low and long. The North 
American species are three in number, the largest of which, Batrachus tau, 
is known as the toad-fish. 
The order Plectognathi, distinguished by the internal union of some of 
the bones of the head, is composed of three families, the Balistine, the 
Ostracionide, and the Gymnodontes. The first of these, the Bautstin a, is 
known by the compressed body and prolonged snout ; the small mouth, 
with a few distinct teeth; the skin roughened by prickles or scales; the 
two dorsals, the first sometimes replaced by a single spine. The ventrals 
are often obsolete, and the pelvic bone is prominent. The three principal 
North American genera are: Balistes, covered with large scales; Mona- 
canthus, with the seales very small; and Aluteres, with the skin covered 
with small and almost invisible granules. 
- In the Osrracionip# the entire body is enveloped by an inferior inflexi- 
ble triangular, or quadrangular, long case, composed of numerous plates 
soldered together, leaving only apertures for the mouth and fins. There 
are no ventral fins, and but a single dorsal. The only North American 
genus of this family is Lactophrys, or trunk-fish, of which there are three 
species. 
The most striking characteristic of the family Gymnoponrzs consists in 
the peculiar structure of the teeth. There are either two, or one, in each 
jaw, occupying its whole extent in a compact mass, and resembling some- 
435 
