210 ME. C. TATE BEGAN ON THE 



8. Plecostomus vaillaxti. 



Plecostomus vaillanti Steiud. Sitzb. Ak. Wien, lxxvi. 1877, p. 225; Eigernn. & Eigenm. Proc. Cal. 

 Ac. (2) i. 1888, p. 169, and Occ. Pap. Cal. Ac. i. p. 407 (1890). 



Depth of body 5J-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 If times, 

 diameter of eye about 6J times, interorbital width 2f times. Length of mandibular 

 ramus about 2J 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. I 7, the first ray as long as the head, 

 the last \ as long ; length of base of dorsal greater than its distance from the adipose 

 fin. A. I 4. Pectoral spine extending to anterior \ of A r entral. Caudal obliquely 

 emarginate. Caudal peduncle of 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 : Eio Puty and Eio Preto, E. Brazil. 



9. Plecostomus emarginatus. 



Hypostomus emarginatus Cuv. & Val. Hist. Nat. Poiss. xv. p. 500 (1840) ; Kner ; Denksclir. Ak. 



Wien, vii. 1854, p. 260. 

 Hypostomus squalinum Schomburgk, Fish. Brit. Guiana, p. 142, pi. iii. (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 scojmlarius Cope, Proc. Ac. Pliilad. 1871, p. 55, pi. xvi. figs. 1 & 2 (nee Cope, t. c. 



p. 286). 

 Plecostomus biseriatus Cope, t. c. p. 285. 

 ? Plecostomus virescens Cope, op. cit. 1874, p. 137, and Proc. Am. Phil. Soc. xvii. 1878, p. 681, and 



ib. xxxiii. 1894, p. 101. 

 Plecostomus villarsi hutk . Overs. Dan. Selsk. 1874, p. 211; Steind. Denkschr. Ak. Wien, xxxix. 



1878, p. 42, pi. vii. 

 Plecostomus tenuicauda Steind. t. c. p. 40, pi. vi., and ib. xlii. 1880, p. 63. 

 Plecostomus anna, Steind. op. cit. xliii. 1881, p. 112, pi. iii. fig. 2. 



Depth of body 6-7 times in the total length, length of head 3-§-4 times. Depth of 

 head lf-2 times in its length, breadth of head 1-g-l-j times, length of snout lf- 

 If times, diameter of eye 5-11 times, interorbital width 2^-2f times. Length of 

 mandibular ramus 3-4 times in the interorbital width. Snout more or less narrowed 



