186 FISHES. 



Ageneiosus, Lacep., 



Have all the characters of a Pimelodus, except that there are no true 

 cirri. 



In some the maxillary bone is turned up into a kind of dentated horn, 

 instead of being continued into a fleshy and flexible cirrus*. 



In others it does not project, and remains concealed under the skin ; 

 the dorsal and pectoral spines are but slightly apparent -j". 



Doras, Lacep. 



These are Machoirans, that is to say Siluri, with a second dorsal, which 

 is adipose, and whose lateral line is mailed with a range of bony plates, 

 each of which is relieved by a spine or salient carina. The dorsal and 

 pectoral spines are very strong and deeply dentated ; the helmet is rough, 

 and continues to the dorsal as in Synodontis, and their shoulder bone 

 forms a point behind. 



Some of them merely have the band of small and crowded teeth in the 

 upper jaw J. 



In others the snout is pointed, and the teeth are either wanting or are 

 hardly visible ; the maxillary cirri are sometimes furnished with lateral 

 setae §. 



Heterobranchus, Geoff. 



Have the head provided with a helmet that is rough, flat, and broader 

 than that of any other Silurus, a circumstance occasioned by two lateral 

 pieces furnished by the frontals and parietals, which cover the orbits and 

 temples. The operculum is still smaller in proportion than in the pre- 

 ceding fishes, and what chiefly distinguishes them from all others is the 

 peculiarity observed by M. GeofFroy, that, besides the ordinary branchiae, 

 they have an apparatus ramifying like a tree, adhering to the superior 

 branch of the third and fourth branchial arch, and which appears to con- 

 stitute a sort of supernumary gills. Their viscera resemble those of other 

 Siluri, and their branchial membrane has from eight or nine to thirteen or 

 fourteen rays. The spine of their pectoral is strong and dentated, but 

 there is none such in the dorsal; their body is naked and elongated, as 

 well as their dorsal and anal. There is no spine in the dorsal. The 

 caudal is distinct. All the species known have eight cirri, and inhabit 



* Silurus militaris, Bl. 362. 



f Sil. inermis, Bl. 363, Seb. Ill, xxix, 8; — Pimel. silondia, Buchan. VII, 50. 



N. B. The Silurus ascita, L., Ad. Fred., pi. xxx, f. 2, is nothing else than a com- 

 mon Pimelodus quitting the egg, the yolk of which has not yet completely entered 

 the abdomen. Linnaeus took this yolk for an ovary, and Block has paraphrased his 

 mistake. It was also, through an error of the press, that Linnaeus is made to place 

 four cirri on the upper jaw — his figures exhibit them on the lower one. 



X Silurus costatus, L., Bl. 376, and Gronov. V, 1, 2, which is also the Cataphractus 

 americanus, Catesb., Suppl. IX, usually quoted as Sil. cataphractus ; — Sil. carinatus, 

 Lacep., which appears to me the same as Gronov. Ill, 4 and 5, generally cited also as 

 the S. cataphractus, and as the Klip-bagre, Marcgr. 174, thus reducing the S. cata- 

 phractus to nothing. — Doras granulosus, Valenc., App. Ilumb. Zool. Obs. II, 133. 



§ Doras niger, Valenc, loc. cit., or Corydoras edentulus, Spix, V ; — Dor. o.ryrhyn- 

 chus, Val., lb. 



