204 siltjrida:. 



before the root of the caudal fin ; the latter but slightly emarginate. 

 Barbels simple ; those of the maxillary extend to the extremity of 

 the humeral process. Eye of moderate size, with the superciliary 

 margin elevated, the interorbital space being concave. Nasal bones 

 with the upper margin finely but deeply serrated. Brownish, fins 

 with dark spots. 



R. Negro, R. Guapore. R. Cupai. 



a. Young. River Cupai. Purchased of Mr. Stevens. 



9. Doras heckelii. 

 Doras heckelii, Kner, Sitzgsber. Wien. Acad. 1855, xvii. p. 125. fig. 4. 

 D. 1/6. A. 12. P. 1/6. L. lat. 29. 



Lateral shields rather low, nearly covered by skin, out of which 

 only the hooks and spines project ; each shield with a series of mar- 

 ginal spines, of which the one nearest to the hook is the largest. 

 Humeral process striated, slender, tapering, not broader than the 

 pectoral spine, and extending to below the third lateral shield. The 

 pectoral spine reaches somewhat beyond the root of the ventral ; 

 dorsal spine serrated only anteriorly, not behind. Caudal fin 

 slightly emarginate. The upper and lower surfaces of the tail are 

 not shielded. Eye of moderate size, superciliary margin not elevated. 

 The maxillary barbels do not extend to the middle of the pectoral 

 spine. Brownish, with darker spots. (Kner.) 



Rio Negro. 



10. Doras cataphractus. 



? Callichthys, sp., Gronov. Mtis. Ichth. i. p. 28. tab. 3. hgs. 4 & 5. 



? Silurus cataphractus, L. Syst. Nat. i. p. 506. 



? Cataphractus americanus, Bl. Schn. p. 107. tab. 28. 



Doras cataphractus, Cuv. ty Vol. xv. p. 276 ; Kner, Sitzgsber. Wien. 



Acad. 1855, xvii. p. 126. 

 ? Doras blochii, Cuv. 8f Vol. xv. p. 277. 

 ? Callichthys asper, Gronov. Syst. ed. Gray. p. 157. 



D. 1/4. A. 9. P. 1/4. V. 6. L. lat. 25-29. 

 Lateral shields very- high, each with a single series of small pro- 

 minent spines along and near the posterior margin. The humeral 

 "process is long, not broader than, and extending to the posterior 

 fourth of, the pectoral spine ; it is tapering and provided with a 

 series of small curved spines. Tail without shields on its upper and 

 lower surfaces. Caudal rounded. Dorsal spine with three slightly 

 serrated ridges, one in front and one on each side ; it is not denti- 

 culated behind. Barbels simple, those of the maxillary extending to 

 the extremity of the humeral process. Eye small. Brownish, with 

 a yellowish band along the middle of the sides of the body and along 

 the median line of the back. Fins with brownish spots. 



Rio Guapore and Rio Negro. 

 a. Skin, 4£ inches long. From Gronow's Collection. — This is not 

 the typical specimen of the species, described and figured by 

 Gronow, I. c. ; he says that he saw it in Seba's Collection : and 



