FISHES OF THE FAMILY L0KICAEIID2E. 235 



Two specimens : Guiana. 



Examples in the Museum at Paris, brought from the La Plata Eiver by d'Orbigny 

 and named H. itacua by Valenciennes, proved to be Plecostomus commersonii C. & V. 

 I have little doubt, however, tbat the species described and figured by Valenciennes is 

 closely allied to Chcetostomus megacephalus Gthr. and may be identical with it. 



18. Ancistrus platycephalus. (Plate XII. fig. 4.) 



Chcetostomus platycephalus Bouleng. Boll. Mus. Torino, xiii. 1898, no. 329, p. 9. 



Depth of body 5f times in the total length, length of head 2f times. Head a little 

 broader than long and 2f times as long as deep. Diameter of eye 11 times in the 

 length of head, interorbitaV" width of times, length of snout If times. Length of 

 mandibular ramus equal to If times the interorbital width. Head without ridges or 

 prominences, flat ; snout very broad, rounded ; interoperculum with 25-30 spines, the 

 longest equal to about f the length of head. Scutes not carinate, the posterior rather 

 strongly spinate, 24 in a longitudinal series, 5 between dorsal and adipose fin, 10 

 between anal and caudal ; supraoccipital bordered posteriorly by a pair of scutes, 

 which exclude the first median scute from contact with it; lower surface of head and 

 abdomen naked. D. I 8, the first ray equal to f the length of head, the last f as long ; 

 length of base of dorsal a little less than its distance from the caudal. A. I 4. 

 Adipose fin well developed. Pectoral spine extending to base of ventral. Caudal 

 obliquely truncate. Caudal peduncle 2f times as long as deep. Olivaceous. 



Total length 140 mm. 



A single specimen: E. Ecuador. 



19. Ancistrus niveatus. 



Hypostomus niveatus Casteln. Anirn. Am. Sud, p. 43, pi. xsi. fig. 3 (1855). 

 Chcetostomus niveatus Giinth. Cat. Fish. v. p. 243 (1864). 

 Hemiancistrus lonffipinnis 1 Kindle, Ann. Ac. N. York, viii. 1895, p. 255. 



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

 Head as broad as long and If times as long as deep. Diameter of eye about 7 times 

 in the length of head, interorbital width 2f times, length of snout about If- times. 

 Length of mandibular ramus about If times in the interorbital width. Snout broad, 

 obtuse; supraorbital edges not raised; supraoccipital flat; temporal plates not 

 carinate ; interoperculum armed with numerous long slender spines, with curved tips, 

 the longest equal to f the length of head. Scutes spinulose, not carinate, 24 in a 

 longitudinal series, 5 between dorsal and adipose fin, 13 between anal and caudal; 

 supraoccipital entirely bordered posteriorly by a single scute ; lower surface of head 

 and abdomen naked. D. I 7, the first ray f the length of head, the last f-f as long, 



1 Professor S. H. Gage, of Cornell University, has kindly sent me a drawing of the type of //. longi- 

 vinnis, which seems almost certainly identical with A. niveatus. 



