I OX ICHTIlYOLOCr 



Teeth subulate and i 



aggregated 



Branchiostegal ravs 



eight or nil 



Dorsal fin situated « 



>ver the inte- 



than long, with one Bpin< 



rns and six 



Adipose fm peduncu 



lated and o 



Anal fin long, and 



provided W 



mences near the anus. 





Ventral tins provide 



d each with 



Caudal tin elongate/ 



1 and quite 



The genus Icialurus 



is at oncer 



pressed, elongated, and s 





ance, very unlike that of 



the stout, o 



Middle States. The hea< 



1 is smaller i 



and not covered by so th 



ick a skill; 



very considerably smalle 



r. But perl 



mode of insertion of the 



supra-occip 



ond interspinal. A firm 





rupted passage from the < 



dorsal fin to 



ICTALURUS SIMPSON II, Gill. 



The body is slender, elongated, and compressed; the height is greatest at the dorsal 

 fin; it is there equal to between a fifth and sixth of the total length from the snout to 

 the concave margin of the caudal; thence it gradually declines for some distance, more 

 rapidly as it approaches the end of the anal tin, the dorsal and especially the abdominal 

 outlines over the anal fm being slightly curved. The caudal peduncle is least high 

 near the middle, where it equals a twelfth of the total length. The greatest thickness 

 is at the bases of the pectoral fins, and is about eight-ninths of the height ; thence it 

 quite regularly diminishes to the compressed and thin base of the caudal fin. 



The head is compressed, and presents in profile an oblong-conical form; from the 

 projecting snout to the margin of the bony operculum it forms twenty-two hundredths 

 of the total length, exclusive of the lobes of the caudal fin. The height, at the vertical 

 of the margin of the operculum, nearly equals a sixth of the total length, and bears the 

 relation to the length of the head of fifteen to twenty-two. The head above is oblong 

 and nearly regularly decreases in width from the pectorals to the snout; at the verti- 

 cal of the eves, it equals three-quarters of the greatest width, and the bony interorbital 

 space only 'equals three-eighths of the same. The head above is transversely arched 

 posteriorly, and beneath is flat 



The eyes are large and oval, mostly situated in the anterior half of the head on 

 the sides. The largest diameter is between a fifth and sixth of the head's length; the 

 interorbital space is double the diameter. 



The maxillarv barbels are slender, and extend beyond the opercula. The nasal 

 barbels are very slender, and are scarcely longer than the diameter of the eye. The 



