80 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY II. 



equal; veutrals each with one simple and seven branched rays ; pectoral 

 fins each with a stout spine, which is commonly retrorse-serrate behind; 

 these serrsB vary much with age and circumstances, and do not appear 

 in this genus to furnish good specific characters; lateral line usually 

 incomplete. 



This genus includes our common Eastern American Catfishes, and is 

 readily recognized by the broad head covered by a thick skin, the free 

 termination of the posterior process of the supraoccipital bone, the 

 compressed body, and by the free adipose fin. 



This genus, although undoubtedly a very natural one, is rather hard 

 to define. Certain species (lupus, niveiventris, nigricans) have real affin- 

 ities with the species of Ichthcelurus, having, like them, the body elon- 

 gate, the head rather narrow, the anal long, the caudal forked, and the 

 coloration iiale. The absence of the connection between the supraoc- 

 cipital and the interspinal is the only technical character by which 

 Amiurus may be distinguished from lohthcElurus. 



ANALYSIS OF SPECIES. 

 *. Caudal fin forked; upper jaw longest; dorsal beginning nearer snout than adipose 

 fin ; colors blackish-silvery : 

 t. Anal fin elongate, of 23 to 28 rays : 

 a. Caudal fin deeply furcate ; head narrow, longer than broad ; anal rays 23 or 24 ; 

 pectoral spines long and slender, dentate ; barbels long; depth 

 about 5 in length ; width of head 4f ; body rather slender : 

 — . Head narrowed, its width being less than its length above; distance from 

 snout to dorsal spine 1^ to 1^ in distance from dorsal spine to 



adipose fin ; base of anal as long as head Lupus, 5. 



— .Head broader, its width equal to its length above; distance to dorsal 

 spine 1^ in distance from spine to adipose fin; base of anal 



notably less than head Niveiventkis, 6. 



aa. Caudal fin strongly furcate ; head 4J in length, its width 5 ; anal rays 25 or 26; 

 pectoral spines dentate, short, and stout; barbels long; body 

 rather stout, color dark, often mottled with pale; size very 



large Nigricans, 7. 



aaa. Caudal fin shallow-furcate ; pectoral spine not serrate ; head broad, as wide 



as long BoREALis, 8. 



tt. Anal fin short and rather low, of 19 to 22 rays ; adipose fin very large; humera 

 process strongly rugose; colors pale, more or less silvery : 

 i. Head narrower, longer than wide, its width 4 to 6 times in length; mouth 

 narrow ; upper jaw much projecting; eye large, 3 to 5 in inter- 

 orbital width ; barbels long, except nasal barbel ; lateral line 

 almost complete ; caudal fin more deeply forked ; anal fin 4^ to 

 5 in length ; dorsal about midway between adipose fin and 



snout Albidus, 9. 



&Z>. Head very broad, as wide as long, its width 3f in length of body ; eye 5 to 6 

 in interorbital width ; caudal not deeply forked ; anal fin 5^ to 6 

 in leugth; mouth wider than in any other species ; jaws nearly 

 equal ; dorsal much nearer adipose fin than snout; colors pale, 

 somewhat silvery, especially on head LoPHius, 10. 



