eigenmann: the FRESHWATER FISHES OF BRITISH GUIANA 235 



Head about' 3; depth 4.5-5; D. 1,7; A. 1,4; plates twenty-four; three or four 

 paired plates between the dorsal, eleven behind the anal; width of head almost 

 equal to its length; interorbital 3.5 in the head, eye 6.5; mandibular ramus 1.4 

 in the interorbital. 



Head convex, without ridges or crest; plates of the body not carinate; oc- 

 cipital truncate where it meets the median plate behind it; interopercle with a few 

 bristles; snout with a swollen margin, sparingly provided with bristles. 



Dorsal spine a little longer than eye and snout; base of dorsal slightly less than 

 its distance from the caudal; caudal oblique, slightly emarginate; ventrals reach- 

 ing to middle of anal; pectorals about to second third of ventrals. 



Nearly uniform dark slaty; dorsal with very faint light areas along the rays. 

 Distal part of caudal slightly lighter, otherwise uniform; pectorals and ventrals 

 in the smaller specimens like the caudal, very faintly blotched in the larger. 



102. Pseudancistrus guentheri Regan. 

 Plecostomus guttatus (not of Cuvier and Valenciennes) Gunther, Catalogue, V, 



1864, 237. 

 Ancistrus guentheri Regan, Trans. Zool. Soc. London, XVII, 1904, 241 (British 



Guiana) . 

 Pseudancistrus guntheri Eigenmann, Repts. Princeton Univ. Exp. Patagonia, 



III, 1910, 409. 



No specimens were collected. It is not certain whether the above references 

 pertain to the area covered by this paper or not. 



Head 3.25; depth 6; D. 1,7; A. 1,4; depth of head 2 in its length, eye 8, inter- 

 orbital 3.33; mandibular ramus 1.25 in interorbital; snout with a broad naked 

 area at its tip; dorsal spine two-thirds the length of the head; pectoral spine not 

 quite reaching base of ventral. Color uniform. 



Xenocara Regan. 

 Xenocara Regan, Trans. Zool. Soc. London, XVII, 1904, 251. — Eigenmann, 



Science, n. s., XXI, 1905, 794. 



Type, Ancistrus gymnorhynckus Kner. 



Interopercle freely movable, usually with spines; snout with a naked margin 

 and without tentacles; mouth narrow, the mandible much less than the width 

 of the interorbital; teeth in the upper jaw about as numerous as those in the lower 



