071 some ne^o or little- known Fishes from Brazil. 9 



II. — On some neio or little-known Fishes obtained hy 

 Dr. J. W. Evans and Mr. Spencer Moore during their 

 recent Expedition to the Province of Matto GrossOj Brazil. 

 By G. A. BOULENGER. 



[Plates I. & II.] 



Plecostomus pantherinuSj Kner. 



Nothing could be more misleading than a division of the 

 fishes of the genus Plecostomus according to the presence or 

 absence of granular plates on the belly. Among the nume- 

 rous specimens of P. hicirrhosus in the British Museum there 

 are some with the belly partly or entirely naked (the latter 

 being young) which are not to be otherwise distinguished 

 from the typical form. Thus, in three specimens (one half- 

 grown and two young) from British Guiana the belly is 

 naked in one young, partly naked in the other, entirely granu- 

 late in the larger specimen. It is therefore very probable 

 that P. seminudusj Eigenmann, will turn out to be merely an 

 individual variation of P. hicirrhosus. With regard to the 

 specimens which I refer to Kner's P. pantherinus, described 

 from a single young specimen from the Rio Guapord, the much 

 larger eye distinguishes them at once from P. hicirrhosus, 

 their nearest ally ; in Kner's specimen, 3 inches long, the 

 eye measures one fourth the length of the head, whereas it 

 measures only one fifth or one sixth in P. hicirrhosus of 

 similar size. In the adult P. pantherinus the diameter of the 

 eye is one fifth the length of the head, against one seventh or 

 one eighth in P. hicirrhosus. The head is besides larger in 

 proportion to the body in the former than in the latter. 



Two specimens were obtained by Dr. Evans in the River 

 Jangada, close to Jangada village ; the larger measures 

 200 millim. (to the end of the middle caudal rays), the 

 smaller 170. 



Form stout. Head as long as broad, one third total length 

 (without caudal) ; snout rounded, with a small naked space 

 at its extremity ; an obtuse ridge from the upper angle of 

 the orbit to below the nostril, the sides of the head below it 

 being slightly concave ; an obtuse ridge on the occiput and 

 another on each side behind the eye ; interoperculum with 

 small spines. Diameter of orbit one fifth length of head, one 

 third length of snout, three fifths to one half interorbital 

 width, and equal to its distance from the posterior border of 

 the head. Labial fold moderate, papillose, not or but slightly 

 notched ; barbel short. Dorsal I 7, the first ray as Ion;? as or 



