from the Essequibo. 443 



beyond, the extremity of the humeral process; the anterior 

 mandibulary barbels are twice or thrice as long as the eye. The 

 numeral process extends backwards beyond the middle of the 

 pectoral spine. Dorsal and pectoral spines serrated, the former 

 along its anterior edge, the latter along both edges ; the dorsal 

 spine is considerably shorter than that of the pectoral fin, the 

 latter being as long as the head, and one-fourth of the total 

 length (without caudal). Caudal fin slightly emarginate, the 

 upper lobe being scarcely longer than the lower. Lateral line 

 irregularly undulated. Uniform brownish black. 



Helogenes (Siluridee). 



Adipous fin very small ; dorsal fin very short, without pungent 

 spine, inserted behind the ventrals ; anal very long. The upper 

 jaw is a little longer than the lower. Barbels six. A band of 

 small teeth in the jaws, and two patches on the vomer. No 

 dermal bones. Eye very small, covered over by the skin. Gill- 

 openings very wide, the gill-membranes being entirely separate. 

 Pectorals without pungent spine ; ventrals six-rayed. 



Helogenes marmoratus. 

 B. 13. D. 5. A. 42. P. 8. V. 6. 

 Only three inches and a half long. 



Crbnuchus (Characinidse) . 



Adipous fin none ; dorsal fin of moderate length, above the 

 ventrals ; anal short ; scales of moderate size ; abdomen rounded; 

 head and body rather compressed, of moderate length. Inter- 

 maxillary and mandible with a single series of tricuspid teeth ; 

 maxillary and palate without teeth ; canine teeth none. Mouth 

 of moderate width. 



Crenuchus spilurus. 



D. 17. A. 11. V. 8. L. lat. 30. 



Dorsal and anal rays somewhat prolonged ; a round, black 

 spot near the root of the caudal fin. 



Lepo7'inus megalepis. 



D. 12. A. 12. L. lat. 33. L. trans. 5/5. 



Body with large blackish spots, arranged in two or three 

 series ; fins red. 



Xiphorhaniphus ferox. 



D. 11. A. 25-26. V. 8. L. lat. 95. 



A large blackish blotch on the shoulder ; the inner caudal 

 rays red, with a black spot in the middle. 



29* 



