95. cn^TOSTOMTjs. 243 



tends to the middle of the ventral. Caudal fin obliquely truncated. 

 Brownish : the upper sm'face of the head and the body with rather 

 irregidar yellowish spots, which are partly confluent into cross-bands. 

 Dorsal fin with three dark longitudinal bands. Lower parts whitish, 

 immaculate. (Kner.) 

 Barra do Rio Negro. 



5. Chaetostomus brachyurus. 



Ancistrus bracliyurus, Kner, Hypostom. p. 279. taf. 4. fig. 1. 

 D. 1/7. A. 6. L. lat. 23. 



Head depressed, without prominence on the occiput, as broad as 

 long, its length being one-third of the total (without caudal) ; eye 

 rather large, its diameter being two-thirds of the ■nddth of the inter- 

 orbital space ; margin of the snout granulated, except in the middle 

 of its extremitj% where it is naked. Interoperculum with about 

 twenty setiform spines, the longest of which are one-third as long 

 as the head. Scutes of the body with a serrated keel ; thorax and 

 belly naked; twelve scutes between anal and caudal. Dorsal fin 

 considerably longer than high, the length of its base being somewhat 

 less than its distance from the caudal. Pectoral spine longer than 

 the head, extending to the middle of the ventral. Caudal fin ob- 

 li(]uely truncated. Brown ; dorsal fin with three dark bands. (Kner.) 



Barra do Rio Negro. 



6. ChaBtostomus itacua. 



Ih-postomus itacua, Valenc. in (VOrb. Voy. Anier. MSrid, Pows.pl. 7. 

 fig. 1 ; Cuv. Sf Val. xv. p. 505 *. 



D. 1/7. A. 5. 



Occiput with a slight prominence. Eye of moderate size, its dia- 

 meter being two-thirds of the width of the interorbital space. Body 

 with light longitudinal bands ; fins with bluish cross-bands. ( V((l. ) 



Rio de la Plata. 



7. Chaetostomus niveatus. 

 Hypostomus niveatus, Casteln. Anim. Am6r. Sud, Poiss. p. 43. pi. 21. 



Hg. 3. 

 ? Hypostomus pictus, Casteln. I. c. p. 44. pi. 22. tig. 2t. 



D. 1/7. A. 5. 

 Dorsal fin considerably longer than high ; caudal obliquely trun- 



* Tliis species is very imperfectly known, the figure given in d'Orbigny's 

 work being indittorently "executed. Kner (Hypostom. p. 281) mentions a species 

 in the Berlin Museum" probably the sanie as that collected by Schoraburgk in 

 British Guiana and determined" by Muller and Troschel. From the notes made 

 by Kner from these specimens, it appears that they belong to a species different 

 from the ifacua of the Rio de la Plata. 



t It \n\\ be better to bury this so-called new species of M. Castelnau among 

 the synonyms, than to carry' it on as a doubtful form, as it is not probable that 

 it will be recognized and characterized at a future time. 



