TELE OS TS. 255 



SILURID^E (upwards of 1,000 species), skin without scales, naked, or 

 covered with bony plates; premaxilla toothed and forming upper jaw; 

 maxilla with barbels. Mostly fresh-water forms from South America and 

 Africa. Amiurus contains our smaller cat-fish (bull-heads or horned pout); 

 closely allied is the nearly blind Gronias from caves in Pennsylvania. 

 Ictalurus, larger river cat-fish. Loricaria and Glorias are armored ; Mal- 

 apterurus of Africa is electric. Fossil siluroids appear in the eocene of 

 Wyoming. 



FIG. 256. Weberian apparatus of the carp, Cyprinus, after Weber, k, sinus 

 impar of ear; r, pneumatic duct ; s, utriculus of ear; /, spinous processes of ante- 

 rior vertebrae; x, Weberian chain, leading to z, the air-bladder. 



CYPRINID/E, narrow mouths, frequently with barbels ; the jaws tooth- 

 less, but with teeth on the pharyngeals, scales cycloid, fins without spines. 

 About 1,000 species in fresh water. Cyprinus, the carp, and Carassius- 

 the gold-fish, come from China. Lencisus and Notropis, numerous. 

 Ptychochrilus of the Pacific coast, 4 feet long. Barbns Cobitis. The 

 Cyprindas appear in eocene. The suckers (CATOSTOMID^:) have sucker- 

 like toothless mouths. About 60 species, mostly from North America. 

 Ictobius, Catostomits. Ainyzon, from American eocene. The CHARA- 

 ciNiDjE {ErythrinuS) Ckaracinns) are tropical. 



The GYMNONOTI of South America are eel-like, the dorsal fin reduced 

 or absent. Gyinnotus electricus, the electric eel. MORMYRID^E, fresh- 

 water, Africa. 



ORDER II. PHYSOSTOMI. 



A duct to the air-bladder, fins without spines, ventral fins 

 abdominal in position ; no Weberian apparatus ; gills comb-like ; 

 scales, when present, usually cycloid 



SUB-ORDER i. ISOSPONDYLI. 



Mostly marine fishes with distinct opercular bones ; shoulder girdle 

 connected with the cranium by a post-temporal ; maxillary and premaxillary 

 distinct, no barbels ; ventral fins sometimes wanting, pharyngeal bones 

 simple. 



