240 MR. C. TATE BEGAN ON THE 



27. Ancistrus barbatus. 



Hypostomus barbatus Cuv. & Val. Hist. Nat. Poiss. xv. p. 506 (1840) ; Schomburgk, Fish. 



Guiana, p. 147 (1841) : Kner, Denkschr. Ak. Wien, vii. 1854, p. 268, pi. ii. fig. 2. 

 Hypostomus guttatus Cuv. & Val. t. c. p. 508. 

 Plecostomus barbatus Giinth. Cat. Fish. v. p. 237 (1864). 

 Pseudancistrus guttatus Sleek. Nat. Verb. Holl. Maats. xx. 1864, Silures de Suriname, p. 10, 



pi. ii. fig. 2, and pi. iii. fig. 3. 

 Pseudancistrus barbatus Eigenm. & Eigenm. Proc. Cal. Ac. (2) ii. 1889, p. 45. . 



Depth of body 5J-5f times in the total length, length of head 3—3^ times. Head 

 a little longer than broad and twice as long as deep. Diameter of eye 5-7-j times in 

 the length of head, interorbital .width 3^-3^- times, length of snout If times. Length 

 of mandibular ramus l|-lf times in the interorbital width. Head without ridges or 

 prominences, flat above ; snout not naked at tip, rounded, its sides margined with 

 bristles, which are short in the female and equal to f the length of head in the male ; 

 interoperculuin moderately movable, armed with similar bristles, which are permanently 

 everted, more numerous in the male. Scutes spinulose, not carinate, 24-25 in a 

 longitudinal series, 6 between dorsal and adipose fin, 11-12 between anal and caudal. 

 Supraoccipital bordered posteriorly by a pair of lateral scutes, and usually to some 

 extent by a median scute. Lower surface of head and abdomen naked. D. I 7, the 

 first ray equal to f-§ -the length of head, the last -f— f as long; length of base of 

 dorsal nearly equal to its distance from the caudal. A. I 4-5. Pectoral spine 

 extending a little beyond base of ventral. Caudal slightly and obliquely emarginate 

 or truncate. Caudal peduncle about 2^- times as long as deep. Brownish, 

 with small white spots on the head, and somewhat larger light spots on body 

 and fins. 



Total length 260 mm. 



Twelve specimens : Guiana. 



28. Ancistrus depressus. 



Chcetostomus depressus Giinth. Proc. Zool. Soc. 1868, p. 232; Steind. Denkschr. Ak. Wien, xliii. 



1881, p. 123, pi. v. fig. 1. 

 Pseudancistrus depressus Eigenm. & Eigenm. Proc. Cal. Ac. (2) ii. 1889, p. 45. 



Depth of body 7 times in the total length, length of head 3 times. Depth of head 

 2\ times in its length, diameter of eye 5 times, interorbital width 4 times. Length of 

 mandibular ramus lj times in the interorbital width. Caudal peduncle 2f times as 

 long as deep. Brownish, with small white spots on head, body, and fin-rays. In all 

 other respects similar to the preceding species. 



Total length 130 mm. 



One specimen : Surinam. 



