408 MEMOIRS OF THE CARNEGIE MUSEUM 



Three specimens, 96-119 mm. Amatuk. (C. M. Cat. No. 1967a; I. U. Cat. 

 No. 12234.) 



One specimen, 152 mm. Tukeit. (C. M. Cat. No. 1968a.) 

 Two specimens, 110-122 mm. Christianburg. (C. M. Cat. No. 1969a; I. U. 

 Cat. No. 12235.) 



One specimen, 85 mm. Erukin. (C. M. Cat. No. 2456.) 

 One specimen, 133 mm. Konawaruk. (C. M. Cat. No. 1970a.) 

 One specimen, 136 mm. Wismar. (C. M. Cat. No. 1971a.) 

 One specimen, 155 mm. to base of caudal. Potaro Landing. (C. M. Cat. 

 No. 1972a.) 



Two specimens, 118-121 mm. Below Packeoo Falls. (C. M. Cat. No. 1973a; 

 I. U. Cat. No. 12236.) 



One specimen, 132 mm. Cluck Island. (C. M. Cat. No. 1974a.) 

 Head 3.5; depth 4.5-5; D. 11; A. 25 in two specimens, 26 in three, 27 in 

 nine, 28 in six, 29 in two. Scales usually 87-89, but ranging from 79-95. 63 Eye 

 4.8 in snout, 4-4.5 in head, 1.3-1.5 in interorbital. 



This species, very similar to A. microlepis, can readily be distinguished from 

 the other species found in Guiana by the very large humeral blotch. The caudal 

 spot is small, well-defined, and circular, confined to the base of the caudal rays in 

 the specimens from Barima, Lama Stop-Off, and Maduni Creek, i. e., in those from 

 the tidal area. In specimens from the interior the humeral spot increases in size, 

 and the caudal spot also becomes larger and more diffuse, extending on the caudal 

 peduncle and frequently to the end of the middle caudal rays. 



The specimens from Lama Stop-Off had the middle of the dorsal orange, two 

 intense orange bands fading out backward on either side of the caudal spot, and a 

 yellow band out from the caudal spot and around it; adipose yellowish. 



262. Acestrorhynchus microlepis (Schomburgk). 

 Hydrocyon microlepis Schomburgk, Fishes Brit. Guiana, I, 1841, 247 (Rio Negro; 



Rio Branco; Essequibo). 

 Xiphorhamphus microlepis Muller and Troschel, Horse Ichth., I, 1845, 18; in 



Schomburgk, Reisen, III, 1848, 636 (Cameroon; Upper Essequibo; Rupununi; 



Takutu). — GDnther, Catalogue, V, 1864, 355 (Essequibo; British Guiana).— 



Steindachner, "Flussfische Sudamerika's, " iv, 1882, 14 (Huallaga; Iquitos; 



Amazons). — Eigenmann and Eigenmann, Proc. U. S. Nat. Mus., XIV, 1891, 



58. 



63 All the specimens but one from Amatuk with fewer than 87 rays. The scales as far so examined are 

 7!) in one, 80 in one, S2 in one, 83 in two, 87 in six, S8 in five, S9 in four, 90 in two, 91 in one, 93 in one, and 

 95 in one. 



