184 FISHES OF ILLINOIS 



bb. Anal rays 17 to 24, including rudiments, seldom more than 23; caudal fin 

 always evidently emarginate. 

 c. Anal rays 21 to 24, Usually 22 or 23, including rudiments; pectoral spine in 

 young with 5 to 10 well-developed strong and sharp teeth on its posterior 

 edge, their length more than half the diameter of the spine, becoming 

 more numerous and relatively much reduced in size in adults, in which 

 they range from 10 to 25; black pigment on anal fin typically densest on 

 membranes near their free margin, in spots forming an obscure longitudi- 

 nal bar near base of fin, or in faint mottlings irregularly distributed on 

 both membranes and rays; in pale unmottled specimens both the mem- 

 branes and the rays about equally pigmented nebulosus. 



cc. Anal rays 17 to 20, usually 18 or 19, including rudiments; pectoral spine 

 at all ages entire or only slightly roughened behind, or (rarely) in adults 

 with 5 to 10 obscure weak and blunt teeth on its posterior edge; outer 

 % of anal membranes uniformly pigmented, always darker than the rays, 

 the fin never mottled or barred or uniformly pigmented on both mem- 

 branes and rays as in c • • melas. 



AMEIURUS LACUSTRIS (Walbaum) 



CATFISH OF THE LAKES* 



Walbaum, 1792, Artedi Pise, 144 (Gadus). 



G., V, 100 (borealis); J. & G., 108 and 882 (Ictalurus lacustris, I. nigricans, [part]); 



M. V., 39 (nigricans, part); J. & E., I, 137; J., 66 (nigricans, part); F., 83 



(Ictalurus nigricans, part); L., 9. 



Large fishes with the tail forked as in Ictalurus and with the occipito- 

 dorsal bridge nearly complete, but with the dark coloration and broad, de- 

 pressed head of Ameiurus; weight ordinarily 5 to 15 pounds, sometimes 40 

 pounds. f Depth 4.5 in length; caudal peduncle stout, its depth 1.6 in its 

 length. Color dark slaty to bluish black above, paler below; without dusky 

 spots; anal dusky-edged. Head broad and depressed, 3.8 in length; width of 

 head 1.2 in its length; interorbital space flat, 1.8 in head; eye 8.3 in head, 4.6 

 in interorbital distance; nose 2.5; upper jaw longer, than lower; maxillary 

 barbels to gill-opening. Dorsal fin 1-6, inserted nearer snout than adipose; 

 dorsal distance 2.7 in length; spine short and bluntly pointed, about as long 

 as nose, its posterior edge not serrate; caudal deeply forked; anal rays 24; 

 pectoral spine about same length as dorsal, weakly serrate behind; humeral 

 process about Yz pectoral spine. 



Described from a single specimen taken at Green Bay, Wis., 

 in 1904. 



This species is peculiar to the Great Lake basin, being com- 

 mon in the Great Lakes and the St. Lawrence River. It was 

 long confused by American ichthyologists with the great blue 

 cat (Ictalurus furcatus) of the Mississippi River. Little is 



* Recent studies by Dr. Evermann (Bull. U. S. Nat. Mus. No. 47, III, 2788) have shown 

 that this species is probably confined to the Great Lakes and the St. Lawrence basin, the speci- 

 mens of "Great Mississippi Catfish''' hitherto- described from the Mississippi under the names 

 nigricans, ponderosus, and lacustris belonging to Ictalurus furcatus. 



f The large size, 150 lb, assigned to the species by Jordan & Evermann (Bull. 47) and by 

 Bean, 1. c, is due to inclusion with it of Bean's A. ponderosus. Jordan and Evermann in the 

 appendix to Pt. III. of Bulletin 47 state that the skeleton of A. ponderosus is that of an Ictalurus. 



