202 MR. C. TATE REGAN ON THE 
; Subfamily I. PLECOSTOMIN &. 
Vertebre below the dorsal fin with bifid neural spines; none of the hemal spines 
bifid; pharyngeals not toothed ; teeth in the jaws in a single series ; pseudobranchie 
present ; upper part of the body protected by bony scutes; caudal peduncle compressed, 
cylindrical, or slightly depressed, with 5 longitudinal series of scutes on each side 
for its whole length; lower transverse part of clavicle and coracoid not exposed ; 
margin of snout naked or covered with small granular plates; anterior rudimentary 
ray of ventral internal and directed forwards. 
Key to the Genera. 
I. First seute of lower lateral series posterior to the temporal plate, with which the second is not 
in contact. 
A. Premaxillaries nearly equal in length to the dentaries and with about the same number 
of teeth. 
1. Operculum and interoperculum little, and not independently, movable. 
Snout granular to its margin. 2. ee ee ee ee ee 1. Plecostomus Gronow. 
Snout witha naked margin . . . ~~ s - + + = + + « «+ 2 Hemipsilichthys¥igmn. 
2. Interoperculum more or less freely movable, usually spinate or bristly. 
a. Snout granular to its margin. 
Teeth numerous, bifid . . . - - + + = + © + + = + « « &. Ancistrus Kner. 
Teeth few, spoon-shaped. 2 6. 6) ee ee ee ee eb Panaque Eigmn. 
6. Snout with a naked margin. 
Mouth wide, the length of mandibular ramus nearly equal to the inter- 
orbital width; naked margin of snout not very wide, without 
tentacles. Lyx ss. en, 3 (bs aR REI nel cs elane ou ina ts 
Mouth moderate or narrow, the length of mandibular ramus considerably 
less than the interorbital width; naked margin of snout wide or 
with more or less distinct tentacles . . . +... +. . « « 6, NXenocara Rgn. 
5. Chetostomus Tschudi. 
B. Premaxillaries much shorter than the dentaries and with 
. Pseudacanthicus Blkr. 
“I 
fewer teeth . 1) +) SCIEee see 
Il. First two scutes of the lower lateral series below the temporal 
plate and in contact with itabove . . . . . . . « » 8, Acanthicus Spix. 
1. PLecosromus. 
Plecostomus Gronow, Mus. i. p. 24 (1758), and Zooph. p. 127 (1763) ; Bleek. Ned. Tijd. Dierk. 1. 
1863, p. 77; Giinth. Cat. Fish. y. p. 230 (1864) ; Eigenm, & Eigenm. Occ. Pap. Cal. Ac. i. 
1890, p. 396. 
Hypostomus Lacép. Hist. Nat. Poiss. v. p. 144 (1803) ; Cuv. & Val. Hist. Nat. Poiss. xy. p, 489 
(1840), part.; Kner, Denkschr. Ak. Wien, vii. 1854, p. 256. 
Rhinelepis Spix, Gen. et Spec. Pisc. Bras. p. 4 (1829) ; Cuv, & Val. Hist. Nat. Poiss. xv. p. 479 
(1840), part.; Giinth, Cat. Fish. v. p. 252 (1864) ; Eigenm. & Eigenm. Occ. Pap. Cal. Ac. i. 
1890, p. 414. 
Body oblong or elongate ; first scute of lower lateral series posterior to clavicle and 
