EIGENMANN: the freshwater fishes of BRITISH GUIANA 197 



base of dorsal and sides of the spine dotted, rest of fin hyaline, except a conspicuous 

 black spot near the tip of the first three dorsal rays. 



Subfamily Auchenipterin^. 

 Centromochlus Kner. 



Centromochlus Kner, SB. Akad. Wiss. Wien, XXVI, 1857, 430 {megalops = 



heckelii). 

 Glanidium {ex Reinhardt, MS.) LtJTKEN, Dan. Vidensk.-Selsk. Skr., XII, 1874, 31 



(albescens) . 



Type, Centromochlus megalops Kner. 



Mental barbels in two pairs; adipose fin shorter than the anal; anal short, 

 7-11; mouth terminal; jaws equal; caudal forked; V. 6. 



67. Centromochlus aulopygius Kner. (Plate XX, fig. 1.) 



Centromochlus aulopygius Kner, SB. Akad. Wiss. Wien, XXVI, 1857, 432, pi. 8, 

 fig. 25 (Rio Guapore). — Gtjnther, Catalogue, V, 1864, 198 (Essequibo).— 

 Eigenmann and Eigenmann, Proc. Cal. Acad. Sci., (2), I, 1888, 157 

 (Cudajas); Occasional Papers Cal. Acad. Sci., I, 1890, 270. — Pellegrin, 

 Bull. Mus. d'Hist. Nat., V, 1899, 158 (Apure).— Eigenmann, Repts. Princeton 

 Univ. Exp. Patagonia, III, 1910, 395. 



One specimen, 65 mm. Creek below Potaro Landing. (C. M. Cat. No. 

 1727.) 



One specimen, 65 mm. Wismar. (I. U. Cat. No. 12643.) 

 Head 3.75-4.25; depth 4-5; D. 1,4 or 1,5; A. 9 or 10; eye 5 in snout, 3 in 

 head, 2 in interorbital. 



Head blunt, bullet-shaped; tail compressed; top of head finely granular; an 

 ovate fontanel, its posterior margin over the last third of the eye; jaws subequal; 

 teeth conical, fixed, in narrow bands; lower margin of gill-opening on a level with 

 the upper margin of the pectoral spine; maxillary barbel reaching slightly beyond 

 the middle of the pectoral spine; mental barbels reaching beyond base of post- 

 mentals, the post-mentals not to base of pectoral. 



Dorsal spine a little shorter than the pectoral spine, as long as the head; 

 anterior margin of dorsal with large antrorse teeth, the posterior margin smooth; 

 pectoral spine serrate on both margins, the teeth of the posterior margin larger. 

 Ventrals not reaching to anal; anal rays crowded, especially in the Wismar speci- 

 men; adipose fin shorter than the dorsal. 



Chocolate brown above, shading to white on the belly; sides of body and 

 caudal with numerous horizontally-oval light spots; lower fins light. 



