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



large, premaxillary with 3 or 4 series of teeth, each tooth with from 3 to 

 5 cusps; teeth in lower jaw in 2 series, the first composed of large tri- 

 cuspid teeth, the second series with 2 canine teeth situated behind ante- 

 rior teeth in first series; maxillary with small tricuspid teeth; nostrils 

 close together; gill-openings wide, the membranes slightly united, free 

 from the isthmus; gill-rakers slender; fontanel present. 



The species of this genus range from Guatemala, south. Four 

 species are found in the region of the Canal Zone. 



KEY TO THE SPECIES. 



a. Scales small, 64 to 80 in lateral series; anal fin long, its base much 

 longer than head, with 32 to 37 rays. 



b. Teeth in lower jaw very large and strong, usually 8, rarely only 

 7 and occasionally 9, in outer series; teeth on outer edge of maxil- 

 lary very small, 9 to 10 in number; 18 to 21 vertical rows of 

 scales crossing back between dorsal and adipose. 



striatulus, p. 294. 



bb. Teeth in lower jaw notably smaller, 13 to 14 in outer series; teeth 

 on outer edge of maxillary moderately developed, 12 to 13 in 

 number; 21 to 25 vertical rows of scales crossing back between 

 dorsal and adipose. chagrensis, p. 295. 



aa. Scales larger, 43 to 58 in lateral series; anal fin short, its base 

 about equal to length of head, with 24 to 30 rays. 



c. Scales moderate, 53 to 58 in lateral series, 16 to 18 vertical rows 

 crossing back between dorsal and adipose; upper jaw strongly 

 projecting, exposing two series of premaxillary teeth anteriorly. 



petrosus, p. 297. 

 cc. Scales large, 43 to 48 in lateral series, 12 to 14 vertical rows cross- 

 ing back between dorsal and adipose; upper jaw only slightly in 

 advance of the lower, the second series of premaxillary teeth well 

 covered by lower lip. argenteus, p. 298. 



40. Brycon striatulus (Kner). 



Chalcinopsis striatulus Kner, Sitzungsb. K. Bayer. Ak. Wiss. Miinchen, 



1863, 226 (Panama); Kner & Steindachner, Abhandl. K. Bayer. 

 ' Ak. Wiss. Miinchen, 1866, 38, PI. V, fig. 2 (New Granada and 



Panama on the Pacific slope ); Gunther, Cat. Fish. Brit. Mus., V, 



1864, 337. 



Brycon striatulus (in part) Jordan & Evermann, Bull. U. S. Nat. Mus., 



XLVII, 1896, 337. 



Head 3.6 to 4.45; depth 3.05 to 3.6; D. 11; A. 32 to 35; scales in 

 lateral series 64 to 73. 



