SOUTH AMERICAN NEMATOGNATHI. 267 



fins nearly of the length, not reaching the veutrals. Grayish, 

 tinged with silvery on the sides. (Gill.) steindachneri 207. 



dd. A. 9 or 10; eye 4 in head. Dorsal plate with its processes ex- 

 tending outward behind. intermedius 208. 

 cc Body with dark spots or bars. 



e. Eye 2f- in the head; pectoral spine longer than the head; fins, ex- 

 cept the caudal, yellow, sides of the body with dark spots. Bones 

 of the head finely granular. Snout very short, rounded. Ante- 

 rior margin of the dorsal spine serrate; pectoral spine serrated 

 along the entire length of both margins. D. I, 5; A. 8; P. I, 5; 

 V. 6. (Steindachner.) perugice 209. 



ee. Eye 4 in the head; pectoral spine as long as the head; dorsal 

 and caudal fins with blackish or whitish spots and dots. 



aulopygius 210. 

 act. Head covered with skin. (GLANIDIUM.) albescens 211. 



206, Centromochlus heckelii. 



Auchenipterus heckelii Filippi, "Guer. Eev. et. Mag. Zool. 166, 1853." 



Centromochlus heckelii Giinther, Cat. Fish. Brit. Mus. v, 197, 1864 

 (copied); Cope, Proc. Am. Philos. Soc. xvii, 677, 1878 (Peruvian 

 Amazon); Vaillant, Bull. Soc. Philom. series 7, iv, 1880 (Calde- 

 ron); Eigenm. & Eigenm. Proc. Cal. Acad. 2d Ser. i, 156, 1888. 

 (Villa Bella; Obidos; Para; Tabatinga; Gurupa; Manacapuru; 

 Lago Alexo; Hyavary). 



Centromochlus megalops Kner, SB. Ak. Wien, xxvi, 430, pi. viii, 

 fig. 24, 1857 (Bogota). 



Habitat: Amazons and tributaries. 



Body slender, terete, tapering backward. Head sub- 

 conical, uniformly arched in transverse profile, except 

 on the interorbital region which is flattish, its width 

 little greater than its depth, 1J in its length. Surface of 

 the bones granular. Dorsal plate continued backward 

 to the second dorsal ray, with an inward projecting pro- 

 cess behind, leaving an arrow-shaped area in which the 

 anterior part of the dorsal fin is situated. Humeral pro- 

 cess long and slender, about reaching the vertical from 

 the posterior margin of the dorsal plate; its surface gran- 

 ular. Fontanel elongate, widest behind. 



Pectoral pore small, situated above the last pectoral ray. 



Maxillary barbel lying in a groove below the eye, 

 reaching about to tip of pectoral spine; mental barbel 

 about as long as the eye, postmentals considerably shorter. 



