176 MEMOIRS OF THE CARNEGIE MUSEUM 



Three specimens, 114-144 mm. Rockstone. (C. M. Cat, No. 1620; I. U. Cat. 

 No. 12020.) 



One specimen, 55 mm. Crab Falls. (C. M. Cat. No. 1621.) 



Head 3.3-3.5; depth 4.4-5.5; D. 1,6; A. 12-13. 



Profile nearly straight, interorbital slightly depressed; surfaces of head covered, 

 scarcely granular in the adult. Dorsal spine slender, smooth or slightly rough in 

 front, not quite equal to snout and eye; last dorsal ray about half the length of 

 the highest, the spine not reaching beyond the middle of the last ray when depressed, 

 usually shorter; base of dorsal a little greater than its distance from the adipose, 

 which is longer than the dorsal ; caudal lobes slender, the upper 3.5-4 in the length ; 

 posterior margin of anal subtruncate; pectoral spine about equal to the snout, 

 with antrorse teeth in front and retrorse teeth behind. Maxillary barbel reaching 

 to base or to tip of caudal, post-mental to middle of pectoral; no teeth on the 

 vomer; humeral process spine-like. Dorsal with a conspicuous black blotch near 

 the middle of the front half of the fin; a light streak from dorsal spine to above 

 ventral and then back to the middle caudal rays, and above this again another 

 light streak. 



49. Pimelodus heteropleurus sp. nov. (Plate XVI, fig. 2.) 



Type unique, 46 mm. Rupununi Pan. (Carnegie Museum Catalog of Fishes 

 No. 1734.) 



Head 4; depth 5.3; D. 1,6; A. 11; adipose 4 in the length; eye 3.3 in the 

 length, but little shorter than the snout, one-fourth longer than width of interorbital. 



Form of Pimelodus clarias, the occipital process narrow at its base, scarcely 

 tapering to its tip, which just reaches the dorsal plate; fontanel not quite reaching 

 to the posterior margin of the eye, a bridge over the middle of the eye, the part 

 back of it narrower, not continued as a groove; jaws equal, the teeth in bands of 

 equal width in the two jaws; maxillary barbels reaching a little beyond middle of 

 adipose, outer mental barbel just beyond base of pectoral. 



Dorsal spine slender, equal to head without snout in length, about equal to 

 the distance between the dorsals; anal rounded; ventrals not reaching anal; pec- 

 toral spine a little longer than the dorsal spine, rough in front, with retrorse teeth 

 behind which increase in size to the middle of the spine, where they cease abruptly; 

 humeral process spine-like. 



Sides punctate, the chromatophores in the median area between the dorsal 

 and anal gathered along the septa; a median series of chromatophores along the 

 sides; back along base of dorsal and between the dorsals dark. 



