232 MR. C. TATE BEGAN ON THE 



Supraoccipital bordered posteriorly by a median scute and by one on eacb side. Lower 

 surface of head and abdomen naked. D. I 7, the first ray f the length of head, the 

 last | 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 i\ 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. 



IS. Ancistkus oligospilus. (Plate XII. fig. 1.) 

 Chcetostomus oligospilus Giinth. Cat. Fish. v. p. 244 (1864). 



Hemiancistrus oligospilus Eigenm. & Eigenm. Proc. Cal. Ae. (2) ii. 1889, p. 43 ; Kindle, Ann. Ac. 

 N. York, viii. 1895, p. 254. 



Depth of body 4-g- times in the total length, length of head 3 times. Head 1-^ times 

 as long as broad and \\ times as long as deep. Diameter of eye 4^ times in the 

 length of head, interorbital width 2-f- times, length of snout If times. Length of 

 mandibular ramus 2f times in the interorbital width. Snout narrowed anteriorly ; 

 supraorbital edges slightly raised ; supraoccipital with low median ridge ; temporal 

 plates not carinate ; interoperculum with about 15 slender spines, the longest equal 

 to 1^ times the diameter of eye. Scutes spinulose, not carinate, 26 in a longitudinal 

 series, 7 between dorsal and adipose fin, 13 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 f as long ; 

 length of base of dorsal considerably more than its distance from the adipose fin. 

 A. I 4. Pectoral spine extending well beyond base of ventral. Caudal emarginate, 

 the inner rays f 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 VITTA.TUS. 

 Chmtostomus vittatus Steind. Denkschr. Ak. Wien, xliii. 1881, p. 115, pi. ii. fig. 5. 

 Hemiancistrus vittatus Eigenm. & Eigenm. 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 4^ times in the total length, length of head 2f 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 2-f- times, length of snout If- times. Length of mandibular 

 ramus 2^ times in the interorbital width. Snout narrowed anteriorly ; supraorbital 



