378 characinid^:. 



the root of the caudal fin. Anal fin with a lobe formed by its middle 

 rays. (Val.) 

 Cayenne. 



17. Myletes setiger. 



Myleus setiger, Mull. Sf Trosch. Hor. Ichth. i. p. 39. taf. 11. fig. 1. 

 Myletes doidyxodon, Cuv. fy Val. xxii. p. 222 ; Casteln. Anim. Amer. 



Sud, Poiss. pi. 34. fig. 1 (bad). 

 setiger, Kner, Denkschr.Acad. Wiss. Wien, 1860, xviii. taf. 2. fig. 6. 



D. 21-22. A. 36-39. V. 8. 



The height of the body is contained once and two-thirds in the total 

 length (without caudal), or twice (the caudal included) ; the length 

 of the head is one -fourth of the total (without caudal). Abdominal 

 serrature composed of from *wenty-eight to thirty-three simple spinous 

 plates. Anterior dorsal rays filiform ; anal bilobed, the point of the 

 second lobe corresponding to the sixteenth ray. Adipose fin small. 

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

 uniform. 



Guianas. 



a. Adult. British Guiana. Presented by Sir R. Schomburgk. — One 



of the typical specimens. 



b. Adult : skin. British Guiana. 



18. Myletes oligacanthus. 



Myleus oligacanthus, Mull. 8f Trosch. Hor. Ichth. i. p. 40. taf. 8. fig. 4 

 (young). 



D. 18-19. A. 36-37. V. 9. 



The height of the body is rather less than one-half of the total 

 length (without caudal), the length of the head somewhat less than 

 one-fourth. There are no prominent spines in front of the ventral, 

 but there is a series of eight or nine strong ones between ventral and 

 vent. Dorsal fin elevated anteriorly. Anal bilobed ; the second lobe 

 is short, and its point is formed by the twenty-seventh ray. Adipose 

 fin small. Gill-rakers of the outer branchial arch soft, filamentous. 

 Scales extremely small. Coloration uniform. 



Guianas. 



a-d. From 7 to 8 inches long : skins. Demerara. Purchased of Mr. 

 Scrivener. 



I have no doubt that our specimens are specifically identical with 

 that described by Miiller and Troschel, although they do not mention 

 the second posterior lobe of the anal fin. The absence of this lobe, 

 which, moreover, is short, may be accounted for by the youth of the 

 specimen in the Berlin Museum. Whether the posterior mandibulary 

 teeth are really absent, or whether they have been only overlooked as 

 in M. setiger, I cannot say, as the greater part of the dentition of our 

 specimens has been taken off by the knife of the collector. 



