448 



ZOOLOGY. 



yvadoi, jaw) is in allusion to the filaments or barbels grow- 

 ing out from the jaws, and which are characteristic of the 

 mcmliers of the group. The upper jaw is formed by the 



intermaxillary bones only, while 

 the supra-maxillary bones form 

 the bases of the large barbels. 

 The suboperculum is always ab- 

 sent, as is also the symplectic ; 

 the supra-occipital and parietal 

 bones are co-ossified. The skin is 

 either naked or with bony plates. 

 The air-bladder connects by a 

 duct with the roof of the oesoph- 

 agus. While a few forms are 

 marine, most of the Siluroid 

 fishes are inhabitants of the riv- 

 ers of trof)ical cou.ntries, a large 

 number being characteristic of 

 the rivers of Brazil. All the 

 North American species belong to 

 the family SiluridcB, of which 

 the common rejiresentatives are 

 the horned pout and western 

 catfish. In these forms the skin 

 is naked. The horned pout, 

 Amiurus atrarius Gill, ranges 

 from N'ew England to Maryland 

 and the Great Lakes. It breeds in 

 New England in holes in gravel during the midsummer. The 

 Great Lake catfish, Amiurus nigricans Lesuenr, is abundant 

 in the Great Lakes, and is about a metre (2-4 feet) in length. 

 The blind catfish, Gronias nigrilabris Cope, inhabits a sub- 

 terranean stream tributary to Conestoga Eiver in Eastern 

 Pennsylvania. 



Among the exotic South American Siluroids ai-e Arms 

 (Fig. 404) and Aspredo (Fig. 405) of Guiana. In Ariusimd 

 some of its allies in South America the eggs are carried by 

 tlic males in their mouth, from five to twenty being thus 



Fig. 40b.—Aspredo, a Siluroid fish, 

 seen from beneath , witti its egg-cap- 

 Bules attached by slight stalks. 



