FISHES OF THE FAMILY LORICARIIDA. 237 
Length of mandibular ramus about 34 times in the interorbital width. Snout broad, 
rounded ; supraorbital edges not raised; supraoccipital flat; temporal plates not 
carinate. Scutes spinulose, not carinate, 22-23 ina longitudinal series, 5—6 between 
dorsal and adipose fin, 9 between anal and caudal. 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 3 the length of head, the last ® as long, joined by a 
membrane to the adipose fin; length of base of dorsal greater than its distance from 
the caudal. A. 14. Pectoral spine stout, bristly, extending to base (young) or 
anterior 3 (adult) of ventral. Caudal obliquely truncate. Caudal peduncle about 
1} times as long as deep. 
Total length 240 mm. 
Three specimens (types of the species, of H. nigricans and I. vicinus respectively) : 
Peruvian Amazon. 
The largest specimen is stuffed and is orange-red in colour; the two smaller ones 
in spirit are blackish. The one named H. vicinus has the spine of the adipose fin 
small, recumbent, and immovably joined to the scute below it. 
22. ANCISTRUS HETERACANTHUS. 
Chetostomus heteracanthus Giinth. Proc. Zool. Soc. 1869, p. 425, figs. 3 & 4. 
Hemiancistrus heteracanthus Kigenm. & Higenm. Proc. Cal. Ac. (2) ii. 1889, p. 44. 
Depth of body 5} times in the total length, length of head 22 times. Head 13 
times as long as broad and twice as long as deep. Diameter of eye 82 times in the 
length of head, interorbital width 1% times, length of snout 13 times. Length of 
mandibular ramus 4 times in the interorbital width. Snout margined with very short 
bristles ; supraorbital edges not raised; supraoccipital flat; temporal plates not 
carinate; interoperculum armed with 12 stout spines, the longest equal to a little 
more than 5 the length of head; external to these, and overlying them, some long 
slender bristles. Scutes spinulose, not carinate, 24 in a longitudinal series, 7 between 
dorsal and adipose fin, 12 between anal and caudal. Supraoccipital bordered 
posteriorly by a median scute and by one on each side. Lower surface of head 
naked; abdomen with some small scattered granules. D.1 7, the first ray equalto 
8 the length of head, the last 2 as long; length of base of dorsal nearly equal to its 
distance from the adipose fin. A.1I 5. Pectoral spine extending to beyond middle of 
ventral. Caudal peduncle 2? times as long as deep. Olivaceous; a blackish spot at 
the base of the first dorsal ray. 
Total length 180 mm. 
One specimen: Peruvian Amazon. 
23. ANCISTRUS PICTUS. 
Hypostomus pictus Casteln. Anim. Am. Sud, p. 44, pl. xxii. fig. 2 (1855). 
Depth of body about 6 times in the total length, length of head 2$ times. Head 
