226 silpbid^:. 



sometimes serrated along the inner edge. Young males, again, have, 

 comparatively, smaller spines than old ones. Several species have 

 the lower (thoracic) portion of the humeral bones much dilated, and 

 either entirely naked, or covered only with thin skin ; these plates 

 are larger in old males than in young ones and in females. In all 

 the species a small space in the middle of the upper surface of the 

 snout remains cutaneoiis, but it is larger, and open in front, in young 

 individuals, whilst it is generally surrounded by bone in mature spe- 

 cimens. 



* Head depressed, broader than high ; sides of the head without bristles. 



1. Callichthys asper. 



Tamoata, Marcgr. Hist. Bras. p. 151 ; Willughby, Lchthyol. tab. N. 18. 



fig. 6. 

 Callichthys, Linn. Amcen. Acad. i. p. 317. tab. 14. fig. 1. 

 Cataphractus barbatus, Klein, 31iss. iv. p. 43. no. 5. 

 Callichthys, sp., Gronov. Mus. Ichtli. i. p. 27, and Zoophyl. no. 389. 

 Seba, iii. tab. 29. fig. 13. 



Silurus callichthys, Linn. Syst. Nat. i. p. 50G. 

 Cataphractus callichthys, Bl, taf. 377. fig. 1; Bl. Schn. p. 107. 

 Callichthys asper, Quo;/ Sf Gaim. Toy. TJran. Zool. p. 232 ; Cm. # Val. 



xv. p. 302 ; Kner, Sitzgsber. Wien. Acad. 1855, xvii. p. 107. 



lseviceps, Cuv. Sy Val. xv. p. 309. 



loricatus, Gronov. Syst. ed. Gray, p. 157. 



B. 4. D.||l. A. 1/6. P. 1/7. V. 6. Vert. 14/13-14. 



No osseous shields between the pectoral fins ; the lower parts 

 naked. Twenty-eight lateral shields in the upper series, from 

 twenty-six to twenty-seven in the lower. A broadish space along 

 the back behind the dorsal fin is naked, but there is a strip of 

 small scales extending forwards from the adipose fin. The shields 

 below the adipose fin reach iipwards nearly to its base. The barbels 

 extend to behind the humeral process. Caudal fin rounded ; pectoral 

 spines covered with fine bristles. Fins with very small blackish 

 specks. 



Brazil and Guianas. 

 a, b, c. Many specimens. Bahia. From Dr. 0. Wucherer's Collection. 

 d. Young. Para. Presented by R. Graham, Esq. 

 e,f. Half-grown. Brazil. Presented by Lord Stuart. 

 g. Adult : stuffed. Brazil. Presented by Mrs. Gragan. 

 h. Adult : skin. From Gronow's Collection. 

 i, Tc. Adult and half-grown. 

 I. Half-grown: stuffed. 

 m. Adult male : skeleton. Bahia. From Dr. 0. Wucherer's Collection. 



2. Callichthys affinis. 

 D.{|1. A. 1/6. P. 1/7. V. 6. 



Very closely allied to O. asper, but with a smaller number of 



