80 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY—II. 
equal; ventrals each with one simple and seven branched rays; pectoral 
fins each with a stout spine, which is commonly retrorse-serrate behind; 
these serre 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 Ichthelurus, having, like them, the body elon- 
gate, the head rather narrow, the anal long, the caudal forked, and the 
coloration pale. The absence of the connection between the supraoe- 
cipital and the interspinal is the only technical character by which 
Amiurus may be distinguished from Ichthelurus. 
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 43; body rather slender: 
—. Head narrowed, its*width being less than its length above; distance from 
snout to dorsal spine 14 to 14 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 14 in distance from spine to adipose fin; base of anal 
notably less'thanwheadss- 2) 22c4 sees see eee NIVEIVENTRIS, 6, 
aa. Caudal fin strongly furcate; head 44 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 
lange: S2ass/5-85 ce Vie a oeeee ee orca sae eae NIGRICANS, 7. 
aaa. Caudal fin shallow-fureate ; pectoral spine not serrate; head broad, as wide 
as lONG Goes Locos. wsscee Ssceeoe cele se seer ee eee 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 : 
b. Head narrower, longer than wide, its width 4 to6 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 44 to 
5 in length; dorsal about midway between adipose fin and 
BNOUU Hts S estas hee cee eee teenie eieetenee ALBIDUS, 9. 
bb. Head very broad, as wide as long, its width 3% in length of body; eye 5 to 6 
in interorbital width; caudal not deeply forked; anal fin 54 to 6 
in length; mouth wider than in any other species ; jaws nearly 
equal; dorsal much nearer adipose fin than snout; colors pale, 
somewhat silvery, especially on head ....-....-... Lopuius, 10. 
