260 MR. C. TATE REGAN ON THE 
Key to the Species. 
I. Pectoral spine extending to base of ventral or a little beyond. 
A. Breadth of head 14-1} times in its length; lower jaw with 
10=15 teeth/onjeach'side: 3. = = “ees ~ cee Up eenoremian anos \0 
B. Breadth of head 1} times in its length; lower jaw with 
6-8 teeth on each side. 
Depth of body 43 times in its length; head, body, and fins with 
blackish’spots! <8". 92°02). . 2“) eet oe 5) ete. oe, Po apc OR EROIRTE 
Depth of body 52-53 times in its length; body and fins with small 
White Spots 4.5 5 Si ede |.) es ee ee es Gog) te ne NOs UE wee eerie 
II. Pectoral spine extending to posterior extremity of ventral . . 4. P. hystrix C. & VY. 
1. PSEUDACANTHICUS SERRATUS. 
Hypostomus serratus Cuv. & Val. Hist. Nat. Poiss. xv. p. 503 (1840). 
Pseudacanthicus serratus Bleek. Nat. Verh. Holl. Maats. xx. 1864, SiJures de Suriname, p. 13, 
pl. i. fig. 2, and pl. i. fig. 1. 
Chetostomus serratus Giinth. Cat. Fish. v. p. 241 (1864). 
Hemiancistrus serratus Kigenm. & Eigenm. Proc. Cal. Ac. (2) ii. 1889, p. 43. 
Depth of body 43-5 times in the total length, length of head 3-3} times. Breadth 
of head 1§-1} times in its length, diameter of eye 7-9 times, interorbital width 
2}-23 times, length of snout 12 times. Lower jaw with 10-15 teeth on each side. 
“4-26 scutes in a longitudinal series. D.1I8; length of base of dorsal equal to its 
distance from the caudal. A. I 5, extending, when laid back, $—+ of the distance from 
its base to the caudal. Pectoral spine extending to base of ventral or a little beyond. 
Caudal slightly emarginate, the outer rays sometimes strongly produced. Caudal 
peduncle 1} times as long as deep. Brown, with small white spots on body and fins. 
Total length 560 mm. 
‘Three specimens: Surinam. 
2. PSEUDACANTHICUS SPINOSUS. 
Hypostomus spinosus Casteln. Anim. Am. Sud, p. 45, pl. xxii. fig. 3 (1855). 
Chetostomus spinosus Giinth. Cat. Fish. v. p. 241 (1864). 
Hemiancistrus spinosus Kigenm, & Eigenm. Proce. Cal. Ac. (2) ii. 1889, p. 43. 
Depth of body 4% times in the total length, length of head 3 times. Breadth of 
head 14 times in its length, diameter of eye 8-10 times, interorbital width 24-31 times, 
length of snout 13-13 times. Lower jaw with 6 or 7 teeth on each side, 26 scutes 
in a longitudinal series. D.18; length of base of dorsal less than its distance from 
the caudal, A. I 5, extending, when laid back, }—4 of the distance from its base to the 
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