Jordan and Ever ma nn. Fishes of North America. 115 



uu Air bladder rudimentary, one division on either side of the coalesced vertebras and entirely 

 surrounded l>y a bony capsule; this capsule formed by the skull and by the lat- 

 eral processes of the anterior vertebra' ; diaphragm wholly osseous, formed by the 

 expansions of the clavicle and scapular process. Scapula and its process firmly joined 

 to the skull. Gill membranes joined to the isthmus; skin covered with bony plates. 

 6. Caudal vertebra; compressed, the neural and ha>mal spines expanded, forming a con- 

 tinuous ridge above and below; skin with several series of plates; mouth inferior, 

 the lower lip reverted; teeth turned abruptly back above and usually expanded; 

 a single scries of teeth erect and in function, the premaxillaries and dontaries box- 

 shaped, filled with numerous relay teeth; intestinal canal coiled; cavity of air 

 bladder communicating with the exterior at a notch in the posterior margin of the 

 temporal plate at beginning of lateral line. LOBICAHIIDJE, xxxv. 



Family XXXIV. SILURIDJS. 

 (THE CATFISHES.) 



Body more or less elongate, naked or covered with bony plates. No 

 true scales. Anterior part of bead with 2 or more barbels, tbe base of 

 the longest pair formed by the small or rudimentary maxillary. Margin 

 of upper jaw formed by premaxillaries only. Suboperculum absent; 

 operculum present. Dorsal fin usually present, short, above or in front 

 of the ventrals. An adipose fin usually present. Anterior rays of dorsal 

 and pectorals usually spinous. Air bladder usually present, large, and 

 connected with the organ of hearing by means of the auditory ossicles. 

 Lower pharyngeals separate. 



After the removal of numerous aberrant forms as distinct families, the 

 family of SILURID/E contains more than 100 genera and upward of 900 

 species. Most of the SILURID^E are fresh-water fishes, inhabiting the 

 rivers of warm regions, particularly South America and Africa; compar- 

 atively few of them are marine, and these few are mostly tropical. They 

 are especially characteristic of the Amazon region in South America. 

 (SILURID.E, part, Giinther, Cat., v, 30-65; 69-220.) 



o. Gill membranes free or forming a free fold across the isthmus, rarely joined to the isthmus; 



anal fin shorter than caudal portion of vertebral column. 

 TACHYSURIN*:: 

 b. Nostrils close together, neither with a barbel, the posterior with a valve; teeth on the 



palate; caudal forked. (Species chiefly marine.) 



c. Lower jaw with 2 barbels; maxillary barbel band-like; pectoral spine with a band- 

 like filament. FELICHTHYS, 08. 

 cc. Lower jaw with 4 barbels; palatine teeth fixed; both jaws with teeth. 

 d. Gill rakers few, 5 to 25; eyes above level of mouth. 



GALEICHTHYS, etc., (genera 69 to 74). 



dd. Gill rakers very many 40 or more, long and slender; eyes scarcely above 

 level of mouth. CATHOBOPS, 75. 



bb. Nostrils remote from each other. (Fresh-water species.) 

 ICTALURIN^E: 



e. Posterior nostril with a barbel; barbels 8; no teeth on vomer or palate. 

 /. Adipose fin with its posterior margin free. 



g. Premaxillary band of teeth truncate behind; not produced backward at 



the outer angles. 

 h. Eyes normal. 



