FISHES — SILURIDAE — PIMELODUS, 207 



The members of this Fub-order are much more mimerous 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 SILURIDAE, Bonap. 



The body is covered with a naked skin, or else protected with bony shields, being always 

 ecaleless. The margin of the upper jaw is formed exclusively by the premaxillar bones, 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 bones 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 bones. 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. 



Sitj.—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, Gov. R^gn. Anim. II, 1817, 199 ; 2d ed. II, le29 ; &, ed. illustr. Poiss. 239.- Gov. & Val. Hist. nat. 



Poiss. XIV, 1839, 310. 

 SUuroidei, (Affasa.), MCll. in Witgm. Archiv fiir Naturg. 1''43, 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 "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 . Ghar . — 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 smootli ; 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. 



Stn .—Pimeio(ius, Linn. Syst. Nat. ed. X, 1758, 304 — Gmel. Linn. Syst. Nat. ed Xllla, 1, iii, 1788, 1353.— Cnv. Rfegn. 

 Anim. II, 1817, 200 ; 2d ed. II, 1829 ; &, cd. Illustr. Poiss. 239.— Richards. Faun. Bor. Amer. Ill, 1836, 

 133.— C0V. & Val. Hist. nat. Poiss. XIV, 1839, 323.— DeKat, 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 be made. On the one hand the body is short and thickish, and the head 



