6 Annals of the Carnegie Museum. 



about 2 x / 2 in the snout, its free portion less than orbit in length, its 

 ventral surface papillose ; maxillary and dentary of about equal length, 

 a little less than ij4, in the interorbital, each jaw with numerous 

 minute teeth. 



Ventral surface entirely naked ; margin of snout in front of base of 

 barbels naked ; predorsal scales not regular ; posterior margin of skull 

 concave on each side of the occipital crest, which is indicated by a 

 point ; no ridges or grooves about the head ; lateral plates straight, not 

 keeled ; a rather broad naked area along the dorsal. 



Origin of dorsal in front of the vertical from the ventrals ; ventrals 

 a little in advance of the middle ; highest dorsal ray reaching to about 

 the middle of the last ray, 4^ in the length; caudal emarginate, the 

 lower lobe slightly longer ; origin of anal under vertical from middle 

 of last dorsal ray ; ventrals reaching middle of anal, pectorals past 

 origin of ventrals. 



Dark, with faint lighter spots ; fin rays dark, the membranes hyaline. 



I take pleasure in naming this species, obtained at my farthest point, 

 for C. Wilgress Anderson, Government Surveyor, an explorer in the 

 Potaro and Roraima regions. 



Lithogenes gen. nov. 



Characters of Plecostomus, the dermal armature reduced to a few 

 ossicles on the back behind the adipose and along a median line from 

 above the origin of the anal to the caudal. 



Lithogenes villosus sp. nov. 



Type unique, 44 mm. (No. 1002 Carnegie Museum Catalog of 

 Fishes.) Aruataima Falls, Upper Potaro. 



Head 3.5 ; depth 7 ; D. 8 ; V. 1,4, P. 1,8 ; eye 6 in snout, 8 in 

 head, 2.75 in interorbital; width of head equals snout and orbit; 

 width behind the pectorals about A greater than the height. 



Oral disk large, margined by a series of incisions ; lips smooth with 

 the faintest rugosities ; a bunch of about twenty-five blunt villi in im- 

 mediate association with the dentary ; barbel equal to prenasal part of 

 the snout measuring from the base of the barbel, free part of barbel 

 equals eye ; a narrow free membrane from the barbel margining the 

 lip outside of the incised inner margin from the barbel to a point 

 behind the angle of the mouth. 



Dentary with two teeth, each with two widely diverging cusps ; pre- 



