PISCES, 83 



Sisor Ham. Buchan. Body naked. Teeth none. First ray of 

 caudal fin produced into a very long seta. 



Sp. Sisor rhabdophorus. Is this its place ? Compare on this fish F. Hamilton 

 Buchanan, Account of the Fishes found in the Ganges, Edinburgh, 1822, 

 4to. 207 — 209; J. E. Gray, Indian Zoology, 1. London, 1834, folio, PL 

 84, fig. I. 



B. Moutli terminal or sub-terminal, under the margin of upper 

 jaw. 



t Operculum immoveable. 



Aspredo L., Gkonov. Body naked, head depressed, with eight 

 or six cirri. Branchial aperture a small fissure. Teeth very small, 

 setaceous, crowded, incurved. Eyes small, superior. Branchioste- 

 gous membrane with five rays. Dorsal fin single, small, nuchal; 

 anal fin long. First ray of pectoral fins very strong, dentate. 



Sp. Aspredo hevisYAJj^yc, Silurus Aspredo L., (Syst. nat.), Amcsn. Acad. 

 I. Tab. II. fig. V. p. 311, Bloch Ichth. Tab. 372, fig. r, Guerin Iconogr., 

 Poiss. PI. 54, fig. I, Cuv. R. Ami., ed. ill., Poiss. PI. 100, fig. i, &c. Fresh- 

 water fishes from Surinam. In many the belly is beset with little stems, to 

 which small round bodies, like eggs, are sometimes attached. 



tt Operculum moveable. {Silurus L. in part.) 



Siluroids proper. — The cranium has iu the mid plane an oblong 

 aperture or fontanelle in front of the frontal bone between it and the 

 sethmoid, and usually another further back between the frontal bone 

 and the interparietal. The teeth are mostly small, card-shaped, and 

 very numerous, placed close together. The subojyerculum is want- 

 ing, and thus the gill-cover consists of thi-ee jDieces only. The num- 

 ber of branchial rays is very various, but the two hindmost, espe- 

 cially the last, are sometimes much broader than the rest, and supply 

 the place in some degree of the suhope7'culum. The fii\st ray of 

 the pectoral fin is in many thick and bony, and is so affixed to 

 an angular articular cavity of the humerus, that the extended ray 

 can be rendered immoveable as by a bolt. Mostly a large, strong, 

 cordiform swimming-bladder is present ; there are no blind append- 

 ages at the inferior aperture of the stomach. 



Many of these fishes live in fresh-water, some as well in rivers as 

 in the sea; but numerous also are the species which, especially in 

 warm regions, must be regai'ded as marine, the species of Arius and 

 Plotosus in the East Indies, &c. 



6-2 



