210 MR. C. TATE REGAN ON THE 
8. PLEcosTOMUS VAILLANTI. 
Plecostomus vaillanti Steind. Sitzb, Ak. Wien, Ixxvi. 1877, p. 225; Eigenm. & Eigenm. Proc. Cal. 
Ac, (2) i. 1888, p. 169, and Occ. Pap. Cal. Ac. i. p. 407 (1890). 
Depth of body 53-6 times in the total length, length of head about 3 times. Depth 
of head 14-2 times in its length, breadth of head 1} times, length of snout 14 times, 
diameter of eye about 64 times, interorbital width 2? times. Length of mandibular 
ramus about 24 times in the interorbital width. Snout rather broad, rounded ; supra- 
orbital margins strongly raised ; supraoccipital with moderately elevated median ridge ; 
temporal plates not carinate; barbel as long as diameter of eye. Scutes spinulose, 
not carinate, 27-28 in a longitudinal series, 7-8 between dorsal and adipose fin, 
14 between anal and caudal. Supraoccipital bordered posteriorly by a median scute 
and by one or two on each side. Lower surface of head and abdomen almost com- 
pletely covered with small granular scales. D.17, the first ray as long as the head, 
the last 3 as long; length of base of dorsal greater than its distance from the adipose 
fin. A.14. Pectoral spine extending to anterior } of ventral. Caudal obliquely 
emarginate. Caudal peduncle 33 times as long as deep. Large dark spots on head, 
body, and fins, those on the fins sometimes forming cross-bars. 
Total length 200 mm. 
Two specimens: Paraguay: Rio Puty and Rio Preto, E. Brazil. 
9, PLECOSTOMUS EMARGINATUS. 
Hypostomus emarginatus Cuy. & Val. Hist. Nat. Poiss. xv. p. 500 (1840); Kner, Denkschr, Ak. 
Wien, vii. 1854, p. 260. 
Hypostomus squalinum Schomburgk, Fish. Brit. Guiana, p. 142, pl. ii. (1841). 
Hypostomus horridus Kner, t. c. p. 259. 
Plecostomus emarginatus Giinth. Cat. Fish. v. p. 233 (1864) ; Eigenm. & Eigenm. Proc. Cal, Ac. (2) 
i. 1888, p. 167, and Occ. Pap. Cal. Ac. i. p. 400 (1890). 
Plecostomus horridus Giinth. t.c. p. 232; Peters, Monatsb. Ak. Berl. 1877, p. 471. 
Plecostomus scopularius Cope, Proc. Ac. Philad. 1871, p. 55, pl. xvi. figs. 1 & 2 (nec Cope, t. c. 
p- 286). 
Plecostomus biseriatus Cope, t. ec. p. 285. 
? Plecostomus virescens Cope, op. cit. 1874, p. 137, and Proc. Am. Phil. Soc. xvii. 1878, p. 681, and 
ib. xxxiil. 1894, p. 101. 
Plecostomus villarsi Liitk. Overs. Dan. Selsk. 1874, p. 211; Steind. Denkschr. Ak, Wien, xxxix. 
1878, p. 42, pl. vii. 
Plecostomus tenuicauda Steind. t. c. p. 40, pl. vi., and ib. xlii. 1880, p. 63. 
Plecostomus anna, Steind. op. cit. xliii. 1881, p. 112, pl. ili. fig. 2. 
Depth of body 6-7 times in the total length, length of head 33-4 times. Depth of 
head 12-2 times in its length, breadth of head 1{-1} times, length of snout 1}- 
18 times, diameter of eye 5-11 times, interorbital width 25-25 times. Length of 
mandibular ramus 3-4 times in the interorbital width. Snout more or less narrowed 
