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 

 oesophagus readily permit a great accumulation of contents. They retain 

 life for a long time after being removed from the water. A curious feature 

 in Lopkius 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, Bati^achus 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 BalistincB, the 

 Ostracionidce, and the Gymnodontes. The first of these, the Balistin^, 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 re*aced 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 scales very small ; and Aluteres, with the skin covered 

 with small and almost invisible granules. 



In the OsTRAciONiD^ 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 Gymnodontes 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 



