270 CALIFORNIA ACADEMY OF SCIENCES. 



caudal, adipose, and base of dorsal fin rusty brown. 

 Young with short whitish streaks along the sides. 



Head 4|-5; depth 5-5i; D. I, 5; A. 10. 



Seven specimens, length .035-. 15 m. Tajapuru; Teffe; 

 Jatuarana; lea; Jutahy; Lago Alexo. 



209. Centromochlus perugiae. 



Centromochhts perngke Steiudachner, Fhissfische Siidam, iv, 29, pi. 



vii, figs. 2-2a, 1882 (Cauelos). 

 Habitat: Canelos. 



210. Centromochlus aulopygius. 



Centroynochlun aulojjijgiuH Kner, SB. Ak. Wien, xxvi, 432, pi. viii, 

 fig. 25, 1857 (Eio Guapore); Giiuther, Cat. Fish. Brit. Mus. v, 

 198, 1864 (Essequibo). Eigeum. & Eigeum. Proc. Cal. Acad. 2,1 

 Ser. i, 157, 1888 (Cudajas). 



Habitat: Eio Guapore; Cadajas; Essequibo. 



Body somewhat compressed. Head short, rounded in 

 front; top of head finely granular; the backward-pro- 

 jecting process of the dorsal plate simple, not turned 

 outward or inward behind. 



Jaws equal, mouth oblique. Maxillary barbel extend- 

 ing to middle of pectoral spine. 



Dorsal spine smooth posteriorly, with strong teeth on 

 its upper half anteriorly. Caudal emarginate. 



Pectoral spine strongly serrate on both margins. 



Humeral process extending beyond middle of pectoral 

 spine. 



Light brownish, mottled with darker; a dark lateral 

 band; dorsal fin dark brown; caudal mottled with 

 darker, a dark longitudinal line on the upper and lower 

 lobes. 



Head 4; depth ^■, D. I, 4; A. 8. 



One specimen .045 m. Cudajas. Thayer Expedition. 



211. Centromochlus albescens. 



Ulanhlium albescens (Reiuhardt MS.) Liitken, Dan. Videu. Selsk. 

 31, 1874 (Eio das Velhas and tributaries); id. 1875, pi. iii, fig. 

 5; Eigenm. & Eigeum. Proc. Cal. Acad. 2d Ser. i, 157, 1888 (Rio 

 Parahyba; Rio Janeiro; Macacos). 



