6G 



Third Sul)family. 

 SILURIDiE ANOMALOPTERiE. 



The rayed dorsal fin is present, but little developed, and belongs 

 to the caudal portion of the vertebral column ; adipose fin exceed- 

 ingly small. The extent of the anal is not much inferior to that 

 of the caudal vertebral column. The giU-membranes overlap the 

 isthmus, remaining separate to the chin. 



South America. 



Fifth Group. HYPOPHTHALMINA. 



The ventral fins are in front of the dorsal. The anterior ver- 

 tebrae are not united into one. 



26. HELOGENES. 



Helogenes, Giinth. Ann. Sf Mag. Nat. Hist. 1863, xii. p. 44.3. 



Adipose 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 pun- 

 gent spine ; ventrals six-rayed. 



British Guiana. 



1. Helogenes marmoratus. 

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



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

 its length being contained five and a half times in the total, without 

 caudal ; it is entirely covered with soft skin. Snout broad, obtusely 

 rounded ; cleft of the mouth of moderate width, the maxillary ex- 

 tending backwards to below the anterior margin of the eye. The 

 trunk and tail are compressed, with the upper and lower profiles only 

 slightly convex ; a longitudinal groove rims along the middle of the 

 back from the nape to the origin of the dorsal fin. The greatest 

 depth of the body is just before the origin of the anal fin, where it 

 is contained four times and a third in the total length (without 

 caudal) ; the least depth of the tail is about one-half of the greatest 

 depth of the body. 



The teeth are minute, cardiform, forming bands in both jaws, the 

 outer series containing somewhat larger and more widely set teeth. 



