eigenmann: the FRESHWATER FISHES OF BRITISH GUIANA 233 



Dorsal spine an orbital diameter less than the length of the head; last dorsal 

 ray attached by an insignificant membrane only; pectoral spine reaching second 

 third of the ventral; ventral to the base of the last anal ray. 



Fins uniformly dusky; sides and back obscurely blotched or banded. 



The adipose is lacking in the cotype. 



Pseudancistrus Bleeker. 



Pseudancistrus Bleeker, Nederl. Tijdschr. Dierk., I, 1863, 78 {barbatus). — Eigen- 

 mann and Eigenmann, Occasional Papers Cal. Acad. Sci., I, 1890, 434. 

 Type, Hypostomus barbatus Cuvier and Valenciennes. 

 Similar to Hemiancistrus, but the sides of the head with bristles, which are 



much larger in the male; interopercle with bristles; an adipose dorsal. 

 A genus with four or five species, of which three are found in Guiana. 



Key to the Guiana Species of Pseudancistrus. 

 a. Length of base of dorsal equal to its distance from the caudal. 



b. Slate-color, with numerous white dots; depth 5.66-6; eye 5 in the head barbatus. 



bb. Uniform slate-color; depth 4.5-5; eye 6.5 in the head nigrescens. 



aa. Length of base of dorsal nearly equal to its distance from the adipose guntheri. 



100. Pseudancistrus barbatus (Cuvier and Valenciennes) . (Plate XXVIII, fig. 3.) 



Hypostomus barbatus Cuvier and Valenciennes, Hist. Nat. Poiss., XV, 1840, 506 

 (La Mana). — Schomburgk, Fishes Brit. Guiana, I, 1841, 147. — Kner, 

 Denkschr. Akad. Wiss. Wien, VII, 1853, 268, pi. 2, fig. 2 (locality ?). 



Plecostomus barbatus Gunther, Catalogue, V, 1864, 237 (Surinam). 



Pseudancistrus barbatus Eigenmann and Eigenmann, Proc. Cal. Acad. Sci., (2), 



II, 1889, 45; Occasional Papers Cal. Acad. Sci., I, 1890, 435; Proc. U. S. Nat. 

 Mus., XIV, 1891, 1842. — Eigenmann, Repts. Princeton Univ. Exp. Patagonia, 



III, 1910, 409. 



Ancistrus barbatus Regan, Trans. Zool. Soc. London, XVII, 1904, 240. 

 Hypostomus guttatus Cuvier and Valenciennes, Hist. Nat. Poiss., XV, 1840, 508 



(Surinam). 

 Plecostomus guttatus Gunther, Catalogue, V, 1864, 237 (British Guiana). 

 Pseudancistrus guttatus Bleeker, " Silures de Suriname," 1864, 10, pi. 2, fig. 2, 



pi. 3, fig. 3 (Surinam). — Eigenmann and Eigenmann, Proc. Cal. Acad. Sci., 



(2), II, 1889, 45; Occasional Papers Cal. Acad. Sci., I, 1890, 435; Proc. U. S. 



Nat. Mus., XIV, 1891, 42. 



Two specimens, 121-140 mm. Crab Falls. (C. M. Cat. No. 1533; I. U. Cat. 

 No. 11968.) 



