FISHES-SILURIDAE-PIMELODUS. 
207 
The members of this pub-order are much more numerous than those of the preceding one ; 
still, all the families are not represented in the waters, whether fresh or salt, of the Western 
States and Territories. 
Family SILXJRIDAE, Bonap. 
The body is covered with a naked skin, or else protected with bony shields, being always 
scaleless. The margin of the upper jaw is formed exclusively by the premaxillar hones, whilst 
the maxillaries are reduced to mere vestiges situated behind the former, or else transformed 
into barbels stretching beyond the angle of the mouth. All the members of this family are 
provided with tentacular barbels, varying in number according to the genera. The gill covers 
or opercular apparatus consists of three hones only: the subopercle being wanting. The handle¬ 
like appendage of the thoracic belt (epicoracoid), observed in the rest of the osseous fishes, is 
also wanting, or exists as a mere process of the said thoracic belt or arch. Their tympanic 
apparatus is composed of two pieces less than in most of the osseous fishes. There are no 
pseudobranchiae or accessory gills. The swimming or air bladder exists in most of them and 
is connected with the organ of hearing through a chain of small auditive hones. The pyloric 
appendages are wanting. The stomach has the form of a sack. In many we observe a very 
stout and serrated bony ray at the exterior edge of the ventral fins. Many, also, are provided 
with an adipose fin besides a true dorsal fin, at the anterior margin of which a strong bony ray 
is likewise often observed. 
Syn. — Siluridae, Bonap. Sagg. distr. meth. anim. vertebr. 1831, 114.— DeKay, New Y. Fauna, IV, 1842, 177.— Storer, 
Synops. 1846, 148 — Agass. Lake Superior, 1850, 278. 
Siluroideae, Richards. Faun. Bor. Amer. Ill, 1836, 132. 
Siluroides, Cuv. Rfegn. Anim. II, 1817, 199 ; 2d ed. II, 1829 ; &, ed. lllustr. Poiss. 239.—Cuv. & Val. Hist. nat. 
Poiss. XIV, 1839, 310. 
Siluroidei, (Agass.), Mull, in fViegm ■ Archiv fur Naturg. 1843, I, 317 
For years past this family has been, on our part, the subject of special investigations, with a 
view of publishing its monograph as the second of our iir Contributions to the Natural History 
of the Fresh water Fishes of North America.” We regret that circumstances will not permit 
us giving in the following pages a full synopsis of all the species so far determined by us. 
No siluroid has as yet been found in the fresh waters of California, Oregon and Wash¬ 
ington Territories ; neither have they been observed in the salt waters of their coasts. 
PIMELODUS, Linn. 
Gen. Char. —Head smooth like the body. Bands of card or velvet-like teeth upon the jaws ; palate toothless. Four pairs 
of barbels : a maxillar pair, which is the longest, and two pairs under the chin, which are longer than the fourth pair arising 
from the edge of the postnasal aperture. Opercular apparatus smooth ; gill openings continuous under the throat. One dorsal 
fin provided anteriorly with a spine ; an adipose dorsal, opposite to which is the anal ; the ventrals being intermediate between 
the latter and the dorsal fin, properly so called. Pectoral and ventral fins provided upon their external edge with a spine. 
Syn.— Pimelodus, Linn. Syst. Nat. ed. X, 1758, 304.— Gmel. Linn. Syst. Nat. ed XHIa, 1, iii, 1788, 1353.—Cuv. Regn. 
Anim. II, 1817, 200 ; 2d ed. II, 1829 ; &, ed. lllustr. Poiss. 239.— Richards. Faun. Bor Amer. Ill, 1836, 
133.—Cuv. & Val. Hist. nat. Poiss. XIV, 1839, 323.— DeIvay, New Y. Faun. IV, 1842, 180.— Storer, 
Synops. 1846, 150.— Agass. Lake Super. 1850, 279. 
The genus Pimelodus , as here restricted, is yet composed of numerous species, of which two 
divisions might he made. On the one hand the body is short and thickish, and the head 
