84 Field Museum of Natural History — Zoology, Vol. X. 



two oblique black bars on each lobe; pectorals and ventrals nearly 

 black mesially. 



Tuyra River basin. 



Brycon argenteus sp. nov. 



Type No. 7588, F. M. N. H.; length 230 mm., Rio Aruza, Aruza, 

 Panama. 



Head 3.7 to 4.0; depth 3.2 to 3.6; D. 10; A. 24 to 26; scales 42 to 45. 



Body elongate, moderately compressed; the profile nearly straight; 

 mouth large, the upper jaw slightly the longer, margin 9f lower lip 

 between the first and second rows of premaxillary teeth; eye 3.2 to 3.5 

 in head; snout 3.8 to 4.2; maxillary 2.2 to 2.4; maxillary teeth 16 or 17 

 on each side; gill-rakers 9 + 12 or 13; origin of dorsal slightly behind 

 that of ventrals; pectorals 1.5 in head; caudal peduncle 2.7 to 2.9. 



Color silvery, darker above; sides without lines or bands; a large 

 black spot on caudal peduncle extending on base of caudal rays. 

 ■ Pacific slope of eastern Panama. 



Brycon petrosus sp. nov. 



Type No. 7589, F. M. N. H.; length 285 mm.; Upper Chagres. 

 Panama. 



Head 3.7 to 3.9; depth 3.5 to 3.7; D. 9 or 10; A. 30 to 32; scales 

 52 to 58. 



Body elongate, robust, moderately compressed; profile concave; 

 mouth large, the upper jaw the longer, the second row of teeth at margin 

 of lower lip; eye 3.6 to 4.0 in head; snout 3.4 to 3.6; maxillary reaching 

 nearly to middle of eye, its length 2.1 to 2.3 in head; maxillary teeth 

 12 or 13 on each side; gill -rakers 10 to 12 + 12 or 13; origin of dorsal 

 slightly in advance of middle of ventrals, about midway between base 

 of caudal and nostril; pectorals 1.4 in head; depth of caudal peduncle 

 2.8 to 2.9 in head. 



Color uniform silvery; sides without dark lines or bands; a large 

 caudal spot extending on base of caudal rays. 



Chagres River basin. 



Roeboides macrolepis sp. nov. 



Type No. 7590, F. M. N. H.; length 56 mm.; Rio Cupe, Boca de 

 Cupe, Panama. 



Head 4.3 to 4.4; depth 3.4 to 3.8; D. I, 7 or 8; A. H, 49 to 54; scales 

 48. 



Body elongate, much compressed ; profile nearly straight ; back not 



