SILURIDZ. 719 
of the species with those previously known. So far as I can judge 
from the figure, this species is an affine of J. robustus, having, like that 
species, the eye anterior and the number of anal rays intermediate (28 
or 29), but differing in the greater slenderness of the body. 
Genus AMIURUS, (Rafinesque) Gill. 
Silurus et Pimelodus sp., LINNaUS, and all writers prior to 1862. 
Ameiurus, RAFINESQUE (1820), Ich. Ohiensis, 65 (as section under subgenus Jctalurus of 
Pimelodus). 
Amiurus, GILL (1862), Prec. Bost. Soc. Nat. Hist. 50, and of recent writers gurcraly. 
Ametirus, Cope (1864), Proc. Acad. Nat. Sci. Phila. 251. 
Gronias, * Cope (1864), Proc. Acad. Nat. Sci. Phila. 231 (G. nigrilabris). 
ETYMOLOGY.—4a, privitive ; uevovpoc, curtailed, in allusion to the entire caudal fin. 
TyPrE.—Silurus cupreus Rafinesque. y 
Body moderately elongated, robust, anteriorly vertically ovate, and 
scarcely compressed; caudal peduncle also robust, but much compressed, 
and at its end evenly convex. ; 
Head large, wide, laterally expanded, above ovate and in profile cunei- 
form; supraoccipital extended little posteriorly and terminating in a 
more or less acute point, which is entirely separate from the second in- 
terspinal buckler; the skin covering the bones is thick. 
Hyes rather small, in one species covered by the skin; mouth large, 
terminal, transverse, the upper jaw in most species the longer; jaws 
often equal, the lower in one or two species distinetly projecting. 
Teeth subulate, aggregated in broad bands on the intermaxillaries 
and dentaries; the intermaxillary band is convex in front, of equal 
breadth, and abruptly truncated near the insertion of the intermaxil- 
laries; the lower dental band is anteriorly semicircular, attenuated to 
the angles of the mouth. 
Branchiostegal membrane on each side with eight or nine rays in 
typical species, ten or eleven in two or three aberrant species; dorsal 
situated over the interval between the pectorals and ventrals, higher 
than long, with a pungent spinous ray dentate behind, and about six 
branched rays; adipose fin short, inserted over the posterior half of the 
anal; anal fin of moderate length, with from fifteen to twenty-six rays, 
the usual number being twenty or twenty-one; caudal fin short, usually 
truncate when spread open, slightly emarginate when not expanded,—in 
species related to Ichthelurus more or less deeply forked, in some other 
species rounded; when the caudal fin is forked the lobes are usually un- 
* Prof. Cope thus defines this genus :—‘‘ Head broad, depressed ; supraoccipital bone 
posteriorly free ; branchiostegal membrane with ten rays; anterior dorsal spine stout: 
posterior (adipose) fin separated from caudal; ventrals with eight rays; eyes rudi- 
mental, covered by the corium; natatory bladder present.” 
