Eigenmann: The Serrasalmin.e and Mylin^. 245 



g. Rooseveltiella stigmaterythraeus (Fowler). 

 Pygocentrus stigmalerytlirceus Fowler, Acad. Nat. Sci. Phila., 191 1, p. 424, fig. 3 

 (La Pedrita, on the Cano Uracoa, Venezuela). 



Known only from the specimens respectively 4 and 5 inches long 

 in the collections of the Philadelphia Academy. They differ from 

 the smaller specimens of notatiis in the large black humeral spot. 



V. Genus Pristobrycon gen. nov. 



Type, Pygocentnim calmoni Steindachner. 



Intermediate in technical characters between the fierce Rooseveltiella 

 without palatine teeth, and the less blood-thirsty Serrasalmo, with a 

 series of permanent teeth along the palate. They are the least 

 destructive of the piranhas. Head short and deep, the snout short; 

 palate with few or no teeth in the adult, the teeth sometimes, as in 

 aureus, more fully developed in the young; cheeks only partly armed; 

 mouth rather narrow, the upper jaw not very oblique, the lower jaw 

 not very prominent. 



Distribution. — Orinoco, Guiana, and Lower Amazon basin. 



Key to the Species of Pristobrycon. 



a. Sides variously spotted. 

 b. Margin of caudal pale. 



c. Depth 1. 6-1. 8; head 3.12-3.66; D. 15-17; A. 32-34; serrae 27-33; 

 interorbital 2.25-2.5 in the head; profile but little depressed over 

 eye; distance from dorsal to caudal equal to length of head, much 

 longer than dorsal; upper half of sides with numerous very small 

 black spots; .2-. 4 of the cheek naked. 



scapular is (Giinther). 10. 

 cc. Depth 1. 6-1. 7; head 3.1-3.75; D. 15-17; A. 32-37; serrae 22-35; inter- 

 orbital 2.16 in the length of head; profile more depressed over eye; 

 distance from dorsal to caudal longer than head; upper half of sides 

 with larger, more or less prominent spots; .25-. 5 of the cheek naked. 



aureus (Agassiz). ir. 



ccc. Depth 1.33; head 3.66; D. 17; A. 40 . .emarginatus (Schomhurgk). 12. 



bb. Margin of caudal dark. Depth 1.4-1.5; head 3.4-3.66; D. 15-16; A. 32 



or 33; serrae 32-33; nearly half of the cheek naked; a small, obscure, 



humeral spot; small, dark spots on the upper half of body. 



calmoni (Steindachner). 13. 

 aa. Numerous dark brown cross-bands dividing below the lateral line into narrow 

 stripes; second suborbital but little higher than eye, its length 1.5 in its 

 height; greatest width of naked area of cheek equal to about one-half the 

 length of the suborbital; head3.33; depth 1.66; D. 17; A.3lor32; serrae 32; 

 interorbital 2.75; origin of dorsal an orbital diameter nearer to snout than 

 the base of the caudal striolalus (Steindachner). 14. 



