23 MR. C. TATE REGAN ON THE 
1} times as long as broad and twice as long as deep. Diameter of eye about 6 times 
in the length of head, interorbital width 2} times, length of snout 12 times. Length 
of mandibular ramus 2} times in the interorbital width. Head very similar to that 
of A, heteracanthus, the interoperculum armed with 12-15 moderately stout spines, 
which are covered by a group of long bristles ; sides of the snout also bearing bristles 
of moderate length. Scutes similar to those of A. heteracanthus both in structure and 
in number. Supraoccipital bordered posteriorly by a median scute and by one on 
each side. Lower surface of head and abdomen naked. D.17; length of base of 
dorsal equal to its distance from the adipose fin. A.I 4. Pectoral spine strong, 
elongate (broken in the type). Caudal peduncle 2? times as long as deep. Large, 
round, light spots on head, body, and fins. 
Length, to base of caudal, 108 mm. 
One specimen, in very bad condition (type of the species): Ucayale, Upper 
Amazon. 
24. +ANCISTRUS MYSTACINUS. 
Ancistrus mystacinus Kner, Denkschr. Ak. Wien, vii. 1854, p. 276. 
Chetostomus mystacinus Giinth. Cat. Fish. v. p. 244 (1864) ; Steind. Denkschr. Ak. Wien, xliii. 
1881, p. 125. 
Hemiancistrus mystacinus Figenm. & Figenm. Proce. Cal. Ac. (2) ii. 1889, p. 43. 
Depth of body about 6 times in the total length, length of head 3 times. Head 
11 times as long as broad. Diameter of eye 7 times in the length of head, interorbital 
width 2} times, length of snout 13 times. Head very similar to that of A. hetera- 
canthus, the sides of the snout with very short bristles, the interoperculum armed with 
about 20 rather stout spines, external to these some long bristles which cover the 
spines when they are retracted. Scutes similar to those of A. heteracanthus in 
structure and number. Lower surface of head and abdomen naked. D. I 7, as high 
as long, the first ray scarcely longer than the ventral. A. 1 5. Pectoral spine 
extending a little beyond the base of ventral. Caudal deeply emarginate. Olivaceous ; 
fins spotted or marbled with darker; lower lobe of caudal blackish. 
The type, from Caracas, is (according to Steindachner) 280 mm, in total length, 
25. ANCISTRUS GUACHAROTE. 
Hypostomus guacharote Cuy. & Val. Hist. Nat. Poiss. xv. p. 508 (1840). 
? Ancistrus guacharote* Gill, Ann. Lye. N. York, vi. 1858, p. 409. 
Chatostomus guacharote Giinth, Cat. Fish. v. p. 245 (1864). 
? Chetostomus trinitatis Giinth. t. ce. p. 246. 
' Dr. Gill has very kindly informed me that the examples which he recorded from Trinidad, and on 
which Dr. Giinther founded (@, trinitatis, cannot be found. Therefore it is still uncertain whether or no the 
species C. trinitatis is valid, 
