THE TRUE FISHES. 169 



Southern waters the ferocious and snake-like Murcena is 

 found, attaining a length of three feet. 



NOTE. In a pond near Wells, on the Maine coast, the eels inva- 

 riably go down into salt water at night, and, as the stream is narrow, 

 the sight is remarkable, thousands filling the channel, leaving the water 

 when alarmed and passing over the dry rocks to the ocean. The sound, 

 a single note; frequently uttered by the eel, is, according to Abbott, 

 more distinctly musical than those made by other fishes, and has a 

 metallic resonance. 



Order III. Thread-jawed Fishes (Ncmatognathi). 

 Cat-Fishes (Silurida). The cat-fishes may be recog- 

 nized by the curious barbels or threads that hang from 

 their jaws. They have no scales, the skin being in some 

 species protected by bony plates. Some are marine, but 

 the majority live in fresh water. A blind cat-fish (Gramas) 

 inhabits a subterranean stream in Pennsylvania. The 

 Arius, of South America, carries its eggs in its mouth, and 

 even the young fish. In a species of Arius, in Panama, 

 the mother first carries them about in a fold of the skin, 

 and later the male receives them in its capacious mouth. 

 The female Aspredo carries its eggs about attached to dang- 

 ling capsules, that cover the fins and ventral surface of the 

 body, disappearing after the breeding season. The com- 



FIG. 209. An electric cat-fish (Malapterus electricus}. 



mon cat-fish carefully guards its young, while the South 

 American Doras and Callichthys build nests of leaves in 

 which the young are placed. These fishes also leave ponds 



