246 silvbuj>m. 



out protuberance in the occipital region ; it is as broad as long, and 

 its length is two-ninths of the total (with the caudal). Scutes stri- 

 ated, not keeled. The diameter of the eye is two-fifths of the width 

 of the interorbital space. The pectoral spine extends beyond the 

 root of the ventral fin ; caudal forked, with the lobes much pointed. 

 Thorax and belly naked. Brownish. ( Val.) 

 Porto Rico. 



13. Chsetostomus trinitatis. 

 Ancistrus guacharote, Gill, Ann. Lye. Nat. Hist. New ¥orfc, vi. p. 409. 

 D. 1/7. A. 4. P. 1/6. 



Head depressed, without protuberance in the occipital region ; it 

 is as broad as long, its length being one-third of the total (without 

 caudal). The diameter of the eye is two-fifths of the width of the 

 interorbital space. Interoptrculum with a tuft of long and slender 

 spines. Scutes of the body not keeled. The distance between the 

 two dorsal fins is only one-half of the length of the base of the first 

 Caudal forked, with the lobes pointed. Thorax and belly naked. 

 Uniform reddish brown. 



Trinidad. 



Mr. Gill says that the species found by him agrees in every par- 

 ticular with H. guacharote of Valenciennes ; but it is evident from 

 the number of the anal rays, which are six in the latter species, that 

 these fishes are different. 



*** Dorsal fins subcontinuous. 



14. Ch&tostomus aurantiacus. 

 Hypostomus aurantiacus, Casteln. Anim.Amer. Sttd, Poiss. p. 43. pi. 21. 

 %• 2. 



D. 1/7. A. 5. V.l/4? 



Head large, depressed, one^-third of the total length (without 

 caudal) ; eye small ; interoperculum with numerous setiform spines. 

 Dorsal fin longer than high ; the membrane behind its last ray ex- 

 tends on to the isolated second dorsal spine. Pectoral spine covered 

 with bristles. Scutes of the body not keeled. Orange-coloured. 

 {Cast.) 



Ucayale. 



15. Chsetostomus nigricans. 



Hypostomus nigricans, Casteln. Anim. Amer. Slid, Poiss. p. 44. pi. 22. 

 fig. 1. 



D. 1/7. A. 5. 



Head broad, depressed, with the snout obtuse ; body and tail short. 

 Interopercular spines long, setiform. Dorsal fin considerably longer 

 than high, the membrane behind its last ray extending backwards 

 to the second dorsal spine. Caudal fin obliquely truncated. (Cast.) 



River Amazons. 



