SILUBID^E. CX. 299 



OEDEE AA. - ISTEMATOGI^ATin. 



(The Sheat Fishes.) 



Skin naked or with bony plates; no true scales; bar 

 bels always present, maxillary bone rudimentary and 

 forming the base of the longest barbel ; margin of upper 

 jaw formed by intermaxillariesonly; sub-opercle absent; 

 air bladder generally present; usually an adipose fin, 

 and in all our species a spine in the dorsal arid pectorals; 

 ventrals abdominal. Chiefly fresh water fishes, apparently 

 related to the Sturgeons. The leading family is Siluridce. 



* FAMILY CX. SILURIDJE. 



(The Cat Fishes.) 



General characters as &quot;above given, ours all have the 

 air bladder well developed, the skin naked, and the 

 dorsal and pectoral spines more or less developed and 

 often serrated behind; the fresh water species have 

 always eight barbels. Genera one hundred or more; 

 species nearly seven hundred; a very large family 

 abounding in the fresh waters of America and the 

 warmer parts of the Old World; a few are marine. 

 Our species, though very numerous, are closely related. 

 * Eyes well developed. 

 f Adipose fin free from caudal. 



$ Dorsal spine well developed ; branchiostegals less than 12. 

 a. Supra-occipital bone connected behind with the base of 

 the dorsal spine ; body slender, elongated ; head rela 

 tively small ; tail strongly forked. . ICTALURUS, 1. 

 aa. Supra-occipital bone free behind ; body short and thick ; 

 head very large, depressed ; caudal rounded (forked in 

 two or three species.) . . . AMIUIUJS, 2. 

 \\ Dorsal spine rudimentary ; branchiostegals 12 ; body elon 

 gated; lower jaw longest. . . HOPLADELUS, 3. 



