238 ME. C. TATE BEGAN ON THE 



ly times as long as broad and twice as long as deep. Diameter of eye about 6 times 

 in the length of head, interorbital width 2-j times, length of snout If times. Length 

 of mandibular ramus 2 j times in the interorbital width. Head very similar to that 

 of A. heter acanthus, the interoperculum armed with 12-15 moderately stout spines, 

 which are covered by a group of long bristles ; sides of the snout also bearing bristles 

 of moderate length. Scutes similar to those of A. heter acanthus both in structure and 

 in number. Supraoccipital bordered posteriorly by a median scute and by one on 

 each side. Lower surface of head and abdomen naked. D. I 7 ; length of base of 

 dorsal equal to its distance from the adipose fin. A. I 4. Pectoral spine strong, 

 elongate (broken in the type). Caudal peduncle 2f times as long as deep. Large, 

 round, light spots on head, body, and fins. 



Length, to base of caudal, 108 mm. 



One specimen, in very bad condition (type of the species) : Ucayale, Upper 

 Amazon. 



24. f Ancisteus mystaciis'US. 



Ancistnis mystacinus Kner, Denkschr. Ak. Wien, vii. 1854, p. 276. 



Cluetostomus mystacinus Giinth. Cat. Fish. v. p. 244 (1864) ; Steind. Denkschr. Ak. Wien, xliii. 



1881, P- 125. 

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



Depth of body about 6 times in the total length, length of head 3 times. Head 

 1^ times as long as broad. Diameter of eye 7 times in the length of head, interorbital 

 width 2|- times, length of snout If- times. Head very similar to that of A. hetera- 

 canthus, the sides of the snout with very short bristles, the interoperculum armed with 

 about 20 rather stout spines, external to these some long bristles which cover the 

 spines when they are retracted. Scutes similar to those of A. heteracanthus in 

 structure and number. Lower surface of head and abdomen naked. D. I 7, as high 

 as long, the first ray scarcely longer than the ventral. A. 1 5. Pectoral spine 

 extending a little beyond the base of ventral. Caudal deeply emarginate. Olivaceous ; 

 fins spotted or marbled with darker; lower lobe of caudal blackish. 

 i The type, from Caracas, is (according to Steindachner) 280 mm. in total length. 



i 25. Ancisteus guaciiaeote. 



Hypostomus guacharote Cuv. & Val. Hist. Nat. Poiss. xv. p. 508 (1810). 

 ? Ancistrus guacharote ' Gill, Ann. Lye. N. York, vi. 1858, p. 409. 

 Cheetostomus gvacharote Giinth. Cat. Fish. v. p. 245 (1864). 

 ? Chatostomus trinitatis Giinth. t. c. p. 246. 



1 Dr. Gill has very kindly informed me that the examples which he recorded from Trinidad, and on 

 ■which Dr. Giinther founded C. trinitatis, cannot he found. Therefore it is still uncertain whether or no the 

 species C. trinitatis is valid. 



