299 



OEDEE AA. NEMATOGUATHL 



(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 and pectorals; 

 ventrals abdominal. Chiefly fresh water fishes, apparently 

 related to the Sturgeons. The leading family is Siluridce. 



FAMILY CX. SILURID^E. 



(The Cat Fishes.) 



General characters as "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. . ICTALUKUS, 1. 



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



head very large, depressed ; caudal rounded (forked in 



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



ft Dorsal spine rudimentary ; branchiostegals 12 ; body elon- 



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



