316 PROOEEIDINGS OF THE N"ATrONAL MUSIEUIM vol.94 



from base of anal to base of midcaudal fin rays 12 (12; 12; 12; 12); 

 plates in front of dorsal fin 4 (4; 4; 4; 4) ; plates from dorsal to origin 

 of adipose fin 6 (6 ; 6 ; 6 ; 6) ; number of spines and bristles on the 

 interopercle about 22 + 22 (23 + 14; 20+15; 21 + 12; 22+18); for 

 additional counts see table 20. 



Head depressed, the interorbital flat, a slightly convex ridge on 

 middorsal line of snout; snout pricldy all over except a small naked 

 area near tip; rarely absent in large adults; width of head at base of 

 pectorals equal to snout and 1}^ to 1% eye diameters; the depressed 

 dorsal extends to origin of adipose or falls short of it by one plate; 

 caudal fin very deeply forked; the shortest middle rays of young 

 one-half length of lower caudal fin ray, w^hich is longest; posterior 

 margin of dorsal fin slightly convex; belly naked to origin of anal 

 fin ; pectoral spines extending about one-third the way along the pelvic 

 spines, a little longer in males than in females; barbel at corners of 

 mouth, shorter than pupU; posterior margin of lower lip finely papil- 

 late and without lappets; length of bony ramus of lower jaw 2}^ in 

 inteorbital space; the interopercle has a rosette of about 20 to 25 

 spines, and aroimd the outer anterior margin of these there are usually 

 10 to 20 long hairlike bristles; each spine and bristle is enclosed basally 

 in a thick dermal sheath that may be expanded distally to enclose the 

 entire spine except its tip; the interopercular spines can be folded dowTi 

 and most of them under the opercle; bristles do not appear to be 

 present m the yomig, and the niunber of bristles increases with size; 

 teeth m jaws bifid, very small and numerous; plates on body not 

 keeled, but they are covered with tiny spinules; the first ray of all the 

 fins is enlarged and covered with spinules; intestine coiled. 



Color. — The general color is grayish, or brownish to blackish brown, 

 with the upper and lower surfaces everywhere with faint pale spots, 

 smaller on the head than posteriorly; these pale spots are absent in 

 the yoimg and sometimes rather obscure in certain adults; no black 

 spots along base of dorsal fin; all fins, except anal and adipose, are 

 barred, the ground color of the fins dark, with the pale spots on the 

 fin rays and not in the membranes between the rays; the number of 

 bars on the fins increases with age, varying from three or four to about 

 six or seven. In some of the smaller specimens there are four or five 

 obscure darkish saddles across the back, one in front of dorsal, the 

 second through front of dorsal fin, third behind base of dorsal, fourth 

 in front of adipose fin and the last under rear of adipose fin; these 

 saddles more or less join to form a dark streak along midsides; lateral 

 line pores white. 



Remarks. — -This new species can be distinguished from all other 

 species with 1,5 anal rays referred to the genus Lasiancistrus by its 

 num.erous (20 to 25) spines on the interopercle, except from L. mys- 

 tacinus Kner, L. caucanus Eigenmann, L. mayoloi Eigenmann, and L. 



