300 MEMOIRS OF THE CARNEGIE MUSEUM 



Type, Leporinus novemfasciatus Spix. 



Head small, conical, the mouth minute, with a few (four to six) teeth in each jaw, 

 directed obliquely forward toward the middle, obliquely truncate or lobed; gill- 

 openings joined to the isthmus. 



The members of the genus are abundant about the rocks and cataracts, and 

 are difficult to catch in the usual ways. 



Key to the Guiana Species of Leporinus. 

 a. A median lateral band reaching from the gill-opening to the caudal, another curving from the eye downward 



and back to the lower edge of the caudal arcus. 



aa. An incomplete lateral band or series of median spots. 



6. Lateral band beginning under the dorsal and extending to the caudal ; lower sides plain. . . nigrotaeniatus. 

 66. Sides with a median series of spots. 



c. First spot most conspicuous, under the dorsal; two spots behind it obscurely connected by a 

 stripe in the young; sometimes one or both of the latter absent ; lateral line 38-40* . . friderici. 

 cc. Spots as under c, but with other spots below, above and in front of them; lateral line 33-34. 



d. Mouth inferior; three teeth in each side of each jaw maculatus. 



dd. Mouth terminal; four teeth in each side of each jaw granti. 



aaa. Sides with vertical bands. 



e. Sides with seven bands, four broad ones and three narrower ones in the interspaces alternus. 



ee. Sides with ten bands in the adult, united in pairs in the young, conspicuous in the young, becoming 

 indefinite with age fasciatus. 



157. Leporinus arcus sp. nov. (Plate XLII, fig. 3.) 

 "Tumany" of the Indians. 

 Type, 206 mm. Tukeit. (Carnegie Museum Catalog of Fishes No. 1832.) 

 Cotypes, two specimens, 397-400 mm. Tukeit, (C. M. Cat. No. 2296; I. U. 



Cat, No. 12122.) 



Three specimens, 64-104 mm. Creek below Potaro Landing. (C. M. Cat. 



No. 1829a; I. U. Cat. No. 12119.) 



One specimen, 49 mm. Tumatumari. (C. M. Cat, No. 1830a.) 



One specimen, 50 mm. Locality ? (I. U. Cat. No. 12120.) 



Two specimens, 59-102 mm. Amatuk. (C. M. Cat. No. 1831a; I. U. Cat, 



No. 12121.) 



Head 3.5-4; depth 3+ ; D. 12; A. 10 or 11; scales 4-36 or 37-4; eye 2.5 



in snout, 5.5 in head, 3 in interorbital in the largest; 1 in snout, 3 in head, 1.25 in 



interorbital in a specimen 64 mm. long. 



Robust, the width a little more than half the length in the adult. Predorsal 



and preventral areas broadly rounded. Snout conical; interorbital very convex 



* In the young of friderici the " spots " appear as a band in process of breaking up into spots. Mrs. 

 C. H. Eigenmann. 



