232 MR. C. TATE REGAN ON THE 
Supraoccipital bordered posteriorly by a median scute and by one on each side. Lower 
surface of head and abdomen naked. D. 17, the first ray $ the length of head, the 
last 2 as long; length of base of dorsal equal to its distance from the spine of the 
adipose fin, A. I 5. Pectoral spine extending a little beyond base of ventral. 
Caudal slightly and obliquely emarginate. Caudal peduncle 4} times as long as deep. 
Brown, with pale spots. Dorsal and caudal with alternate dark and light spots on 
the rays. 
Total length 170 mm. 
A single specimen: R. Amazon, 
13. AncisTRus OLIGOSPILUS. (Plate XII. fig. 1.) 
Chetostomus oligospilus Giinth. Cat. Fish. v. p. 244 (1864). 
Hemiancistrus oligospilus Bigenm. & Eigenm. Proc. Cal. Ac. (2) ii. 1889, p. 43; Kindle, Ann. Ac. 
N. York, viii. 1895, p. 254. 
Depth of body 4} times in the total length, length of head 3 times. Head 1} times 
as long as broad and 1} times as long as deep. Diameter of eye 4} times in the 
length of head, interorbital width 2 times, length of snout 1? times. Length of 
mandibular ramus 2% times in the interorbital width. Snout narrowed anteriorly ; 
supraorbital edges slightly raised ; supraoccipital with low median ridge; temporal 
plates not carinate ; interopereulum with about 15 slender spines, the longest equal 
to 1} times the diameter of eye. Scutes spinulose, not carinate, 20 in a longitudinal 
series, 7 between dorsal and adipose fin, 15 between anal and caudal. Supraoccipital 
bordered posteriorly by a median scute and by one on each side. Lower surface of 
head and abdomen in the young naked, except for a granular strip between the 
pectorals. D. I 7, the first ray a little longer than the head, the last } as long ; 
length of base of dorsal considerably more than its distance from the adipose fin. 
A.14. Pectoral spine extending well beyond base of ventral. Caudal emarginate, 
the inner rays 2 as long as the outer, which are equal to the length of head. Caudal 
peduncle 3 times as long as deep. Large round dark spots on head, body, and fins, 
those on the head and the lower surface somewhat smaller than the others, 
Total length 107 mm. 
One specimen: R. Capin. 
14, ANCISTRUS VITTATUS. 
Chetostomus vittatus Steind. Denkschr. Ak. Wien, xliii. 1881, p. 115, pl. i. fig. 5. 
Hemiancistrus viltatus Eigenm, & Figenm. Proc. Cal. Ac. (2) ii. 1889, p. 44, and Occ. Pap. Cal. 
Ac. i. 1890, p. 421 ; Kindle, Ann. Ac. N. York, viii. 1895, p. 254. 
Depth of body 44 times in the total length, length of head 2$ times. Head 1} times 
as long as broad and 1} times as long as deep. Diameter of eye 5 times in the length 
of head, interorbital width 24 times, length of snout 13 times. Length of mandibular 
ramus 2} times in the interorbital width. Snout narrowed anteriorly ; supraorbital 
