312 CALIFORNIA ACADEMY OF SCIENCES. 



This genus differs from Hypophthalmus in having a 

 band of teeth in the jaws and two patches on the vomer. 



Eye small, covered with skin, above the level of the 

 angle of the mouth. 



Adipose fin very small; dorsal fin very short, without 

 pungent spine, inserted behind the ventrals; anal very 

 long. Barbels six. No dermal bones. 



Gill-membranes entirely separate; pectorals without 

 spine; ventrals six-rayed. Branchiostegals 13. 



247. Helogenes marmoratus. 



Hcloijfncn marmoratus Gtiutlier, 1. c. (Essecpiibo); id. Cat. Fish. 



Brit. Mus. V, 66, 1864 (Essequibo). 

 Habitat: Essequibo Kiver. 



Head small, slightly depressed, short, two-thirds as 

 broad as long. Snout broad, obtusely rounded; mouth 

 of moderate width. 



Body compressed, upper and lower profiles only 

 slightly convex; a longitudinal groove from nape to 

 origin of the dorsal. 



Teeth minute, cardiform, forming bands in both jaws, 

 the outer series containing somewhat larger and more 

 widely set teeth; two patches of teeth on the vomer. 



Barbels thin, and of nearly equal length, extending 

 to, or nearly to, the middle of the pectoral fin; post- 

 mental barbels close behind the mentals and almost be- 

 low the maxillary barbels. 



Dorsal fin a little behind the middle between the nape 

 and the caudal; its height shorter than head. Adipose 

 fin very short. Caudal equally lobed; 5 in the length. 

 Anal with fieshy base; extending to root of caudal. 

 Pectoral equal to the head in length, extending be- 

 yond the base of the ventral fin; ventral fin extending 

 slightly beyond origin of anal. 



Blackish brown, finely marbled with black. HeadSi; 

 depth 4i. Br. 13; D. 5; A. 42. (Gunther.) 



