280 ME. C. TATE REGAN OX THE 



Key to the Si)ecies. 



m 



I. Pectoral spine extending to base of ventral or a little beyond. 



A. Breadth of head 1^— li times in its length- lower jaw with 



10-15 teeth on each side 1. P. serratus C. & V. 



B. Breadth of head 1\ times in its length; lower jaw with 



6-8 teeth on each side. 

 Depth of body 4§ times in its length; head, body, and fins with 



blackish spots 2. P. spinosvs Casteln. 



Depth of body 5?-5-| times in its length; body and fins with small 



-white spots 3. P.fordii Gthr. 



II. Pectoral spine extending to posterior extremity of ventral . . 4. P. hystrix C. & V. 



1. PsEUDACANTHICUS SEEEATUS. 



Hypostomus serratus Cuv. & Val. Hist. Nat. Poiss. xv. p. 503 (1840). 



Pseudacanthicus serratus Bleek. Nat. Verb. Holl. Maats. xx. 1864, Silures de Suriname, p. 13, 



pi. i. fig. 2, and pi. iii. fig. 1. 

 Chtetostomus serratus Giinth. Cat. Fish. v. p. 241 (1864). 

 Hemiancistrus serratus Eigenm. & Eigenm. Proc. Cal. Ac. (2) ii. 188'J, p. 43. 



Depth of body 4f- 5 times in the total length, length of head 3-3-^ times. Breadth 

 of head 1^-1-g- times in its length, diameter of eye 7-9 times, interorbital width 

 2-|~2f times, length of snont If times. Lower jaw with 10-15 teeth on each side. 

 24-26 scutes in a longitudinal series. D. I 8 ; length of base of dorsal equal to its 

 distance from the caudal. A. I 5, extending, when laid back, f — f 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 If times as long as deep. Brown, with small white spots on body and fins. 



Total length 360 mm. 



Three specimens : Surinam. 



2. Pseudacanthicus spinosus. 



Hypostomus spinosus Casteln. Anim. Am. Sud, p. 45, pi. xxii. fig. 3 (1855). 



Chtetostomus spinosus Giinth. Cat. Fish. v. p. 241 (1864). 



Hemiancistrus spinosus Eigenm. & Eigenm. Proc. Cal. Ac. (2) ii. 1889, p. 43. 



Depth of body 4f times in the total length, length of head 3 times. Breadth of 

 head 1^ times in its length, diameter of eye 8-10 times, interorbital width 2f— 3y times, 

 length of snout lf-l| times. Lower jaw with 6 or 7 teeth on each side. 26 scutes 

 in a longitudinal series. D. 1 S ; length of base of dorsal less than its distance from 

 the caudal. A. I 5, extending, when laid back, f— § of the distance from its base to the 



