and its Tributaries. 273 
closer examination renders it certain that it is not that 
species. 
In the peculiar form of its mouth it resembles some of the 
Catostomi, but the form of the body and fins more nearly 
assimilate it to the genus under which we have placed it. 
We usually find it associated with the Semotilus biguttata, 
and in the habits of the two there is a strong resemblance. 
C. nigricans. Le Sueur. Mullet. Mud Sucker. 
p. 102. 
The Black Sucker. Storer’s Rep. on Fishes of Mass. p. 86. 
Kirtland's Report, pp. 169, 193. 
- g The Black Sucker. Dekay’s Rep. p. 202. 
y x " Hist. Nat. des Poiss. t. xvii. p. 453. 
Catostomus nigricans. Le Sueur, Jour, Acad. Nat. Sc. Vol. I. 
se « 
e 
Plate XXI. Fig. 3. 
Head large, quadrangular, more than one-fifth of the total 
length of the fish ; eyes oblong, with a profound impression 
neath. 
Body subquadrangular at its junction with the base of the 
head ; cylindric and tapering from the dorsal-fin to the tail ; 
abdomen full and rounded. 5 
Dorsal fin quadrangular, elevated before. 
Caudal fin deeply lunate. 
Anal fin, at its tip, reaches the base of the caudal. 
Ventral fin falcate, extends beyond the dorsal. 
mU ectoral reaches as far back as the commencement of the 
Color. - The back and head dusky brown ; sides olive and | 
wn, blotched with 4 or 5 transverse dusky brown bars, 
Which are interrupted in their course on the sides; abdomen 
and sides cupreous ; sides of the head iridescent and cu 
Length 12 to 16 inches. 
7/00. Every permanent stream in the west. 
D.11; C.18; A.8; V. 9; P. 18 rays. - 
Servations. 'Thisis the most common species of Sucker, 
