376 CHARACINID.E. 



almost regular ellipse. Snout obtuse, rather shorter than the eye, 

 the diameter of which is two-sevenths of the length of the head ; the 

 width of the interorbital space is not quite twice the diameter of the 

 eye. Dentition as normally in this genus. The naked space on the 

 cheek is higher than the second infraorbital bone. The abdominal 

 serrature is composed of from forty-one to fifty-one closely-set spinous 

 plates. Dorsal fin with the anterior rays not prolonged ; it com- 

 mences midway between the extremity of the snout and the end of 

 the lateral line, and the length of its base is a little more than one- 

 third of the total (without caudal). Adipose fin very short, its length 

 being only one-half of its distance from the dorsal fin. Anal fin 

 obtusely bilobate : the third ray is rather broad, cartilaginous, and 

 about half as long as the head ; the point of the second lobe corre- 

 sponds to about the twenty-first ray. Caudal slightly emarginate. 

 Gill-rakers of the outer branchial arch short, lanceolate. Coloration 

 uniform, or body with scattered round rose-coloured spots. 

 British Guiana. 



a. Nine and a half inches long. Presented by Sir R. Schomburgk. 

 6. Fine specimen. Essequibo. From Mr. Ehrhardt's Collection. 



11. Myletes divaricatus. 



Cuv. 8f Val. xxii. p. 215 ; Kner, Denkschr. Acad. Wiss. Wien, 1860, 

 xviii. p. 23. 



D. 23. A. 33. 



Rays of the dorsal fin produced into filaments ; anal fin bilobed, 

 the second lobe being formed by the prolongation of the fourteenth 

 to twenty-fourth rays. (The anal rays are bifid at their extremity, 

 one part being bent outwards to the right-hand side, the other to 

 the left*.) {Val.) 



Essequibo. 



12. Myletes hypsauchen. 



Midi. 8,- Trosch. Hor. Ichth. i. p. 38. tab. 10. fig. 1 ; Cuv. fy Val. xxii. 

 p. 219 ; Kner, Denkschr. Acad. Wiss. Wien, 1860, xviii. p. 26. 



D. 19. r A. 39-43. V. 7. 



The height of the body is four-fifths of the total length (without 

 caudal), the length of the head one-fourth. Abdominal serrature 

 composed of twenty-nine or thirty spinous plates. Anterior dorsal 

 rays rather high ; anal fin with the margin undulated, its anterior 

 rays not prolonged. Adipose fin long, the length of its base being 

 three-fourths of that of the dorsal fin. Gill-rakers of the outer bran- 

 chial arch long, setiform. Coloration uniform. 



Essequibo River. 



a. One of the typical specimens. Presented by Sir R. Schomburgk. 



b. Half-grown. From the Collection of the Zoological Societv. 



* It is probable that this peculiarity is found only in some individuals. 



