338 MEMOIRS OF THE CARNEGIE MUSEUM 



Head 3.5-3.75; depth 3.25-3.50; D. 11 ; A. 12-14; scales 5-30 to 32-3; eye 2.33 

 in the head; snout two-thirds of the eye; interorbital less than the eye, about 

 2.75 in the head. 



Humeral spot distinct but not heavy, not conspicuously elongate. Lateral 

 stripe (probably red in life) the width of one scale, not so intense as the humeral 

 spot, expanded on the caudal peduncle, but not extending upon the fin; scales 

 overlying the lateral stripe distinctly silvery. First five anal rays, the caudal, 

 and all of the dorsal, dusky. Each median dorsal scale with a roundish dark spot. 

 Scales of the upper half of the sides outlined with dusky. A few chromatophores 

 scattered about the base of the anal and aggregated so as to form a small dark spot 

 or line on the ventral side of the caudal peduncle. 



Hyphessobrycon Durbin. 

 Hyphessobrycon Durbin, Bull. Mus. Comp. Zool., LII, 1908, 100. 



Type, Hyphessobrycon compressus Meek. 



Having" the characters ot Hemigrammus, but the caudal naked. 



The account of this genus is compiled from a manuscript by Mrs. Marion Durbin 

 Ellis. 



Key to the Guiana Species of Hyphessobrycon. 



a. Dorsal with a well-defined black spot. 



b. Humeral spot present; anal not marked with black, or with black only on the tips of the rays. Second 



suborbital covering the entire cheek. Last few, and frequently the first few, anal rays with black 

 on or near their tips. Humeral spot very small. Depth 3.8: head at base of occipital process 

 three-fourths the greatest, depth. Maxillary with two or three tricuspid teeth; inner row of pre- 

 maxillary of five teeth. D. 11; A. 26; scales 5-32 to 34-3 minor. 



bb. No humeral or caudal spot; the black dorsal spot margined with white above. Maxillary with four 



to six tricuspid or conical teeth. D. 11 ; A. 26 or 27; scales 5-31 to 33-3 rosaceus. 



aa. Dorsal plain. 



c. No humeral spot. 



d. A small black chevron at the base of each caudal lobe. A row of small black spots along the 

 base of the anal. Maxillary with six small teeth. Ten to twelve small conical or tricuspid 

 teeth in the second row of the premaxillary. D. 11; A. 19 or 20; scales 4-31-3. . .riddlei. 

 dd. Caudal sometimes plain, sometimes with a faint spot. Maxillary with two minute teeth. Pre- 

 maxillary with five three- to five-pointed teeth in the second row. D. 10 or 11 ; A. 17 to 24; 



scales .5-29 to 34-3.5 to 4 gracilis. 



(/</«/. Maxillary with two or three broad, five- to seven-pointed teeth; premaxillary with five five- to 

 seven-pointed teeth in the inner row. A black lateral stripe, somewhat diffused in the 

 humeral region; caudal spot continued on the middle rays, but not to their end. D. 11; A. 



1 (i or 17; scales 5-30 to 33-3 minimus. 



cc. Both humeral and caudal spots developed. (See also minimus.) Lower part of caudal peduncle 

 dark, the upper part of the peduncle light; second suborbital broad, in contact, or nearly in 



