EIGENMANN: the freshwater fishes of BRITISH GUIANA 211 



aa. Gill-membranes scarcely united to the isthmus, extending much farther below than above the pec- 

 toral; posterior margin of the eye near the middle of the head; ventrals reaching bej^ond anus; 

 more slender; chromatophores of the sides radiating in all directions; maxillary barbels reaching 

 the tip of the opercle, but little shorter than the head; mental barbels reaching the edge of the 

 gill-membrane, post-mentals a little beyond the edge of the gill-membrane when laid straight 

 back minutus. 



80. Hemicetopsis macilentus sp. nov. (Plate XXIII, fig. 1.) 



Type, 55 mm. Creek below Potaro Landing. (Carnegie Museum Catalog 

 of Fishes No. 1726.) 



Cotype, 65 mm. Creek below Potaro Landing. (I. U. Cat. No. 12100.) 



Head 3.33; depth 3.8; D. 1,5; A. 23, V. 6; P. 1,7; eye 3 in snout, 8 in head, 

 3 in distance between the eyes. 



Head short, blunt; tail compressed; width of head equals its length without 

 the snout; head covered with loose skin, which is minutely papillose; upper jaw 

 projecting, the mouth wide, 1.5 in the length of the head; teeth hard, conical, those 

 in the jaws in narrow bands, those on the vomer larger, in a single series, with some- 

 times an extra tooth near the end of the row; maxiUary barbel about half the 

 length of the head; space between gill-openings 2.5 in the length of the head. 



Dorsal spine a little less than one-third the length of the head; caudal fin 

 short, forked, the lobes about 4.5 in the length; ventrals free from each other and 

 from the belly; pectoral spine about one-fifth of the length of the head. 



Upper surface of head gray; sides with numerous chromatophores, whose rays 

 branch forward and backward from the center of the cell, giving a strigose effect 

 and looking like little bundles of sticks tied in the middle, hence the name. 



81. Hemicetopsis minutus sp. nov. (Plate XXIII, fig. 2.) 



Type unique, a specimen 22 mm. long. Amatuk Cataract. (Carnegie Mu- 

 seum Catalog of Fishes No. 1728.) 



Differs from macilentus in having the color-cells regularly stellate, the ventrals 

 reaching to origin of anal (to anus in H. macilentus) and the gill-membranes very 

 narrowly united to the isthmus, almost free; barbels all reaching the gill-opening 

 when laid straight back; posterior margin of the eye near the middle of the head 

 (at the end of the first third in H. macilentus). 



Subfamily PYOiDiiNiE. 

 Pygidium Meyen. 

 Trichomycterus Valenciennes, in Humboldt, Rec. Obs. Zool., II, 1833, 348 

 {nigricans), not Thrichomycterus Humboldt. 



