286 FIELD MUSEUM OF NATURAL HISTORY ZOOLOGY, VOL. X. 



of anal decurrent, with several interpolated rows; origin of dorsal fin 

 about midway between tip of snout and base of caudal; adipose fin well 

 developed, over posterior fifth of anal, a little nearer base of caudal than 

 base of last dorsal ray; caudal fin forked, the lobes of about equal length; 

 anal fin rather long, its base 2.8 to 3.25 in length of body, its origin 

 under posterior rays of dorsal, midway between posterior margin of 

 eye and base of caudal; ventral fins scarcely reaching origin of anal, 

 inserted an eye's diameter nearer tip of snout than base of last anal 

 ray; pectoral fins reaching to or slightly past base of ventrals, only 

 slightly shorter than head. 



Color silvery; sides with a plumbeous lateral band, darkest poste- 

 riorly; faint humeral and opercular spots present; a black band extend- 

 ing from base of caudal to tips of middle caudal rays. 



Of this species there are 66 specimens, ranging from 40 to 80 mm. in 

 length, in the present collection. All were taken in the Rio Tuyra 

 Basin. We have designated as the type a specimen, 65 mm. in length, 

 from the mouth of the Rio Yape. 



Considerable variation in the depth of the body and the number of 

 teeth on the maxillary is apparent among our specimens, but these 

 appear to be only individual variations. 



This species differs from H. decurrens (Eigenmann), of which we have 

 examined a paratype, in the fewer scales in the lateral line, in the slightly 

 shorter and more posteriorly placed anal. In H. decurrens there are 44 

 scales in the lateral line, 31 to 33 anal rays and the origin of the anal 

 is in front of the middle of base of dorsal. This species is also closely 

 related to H. guppii (Regan) from which it apparently differs in having 

 one more row of scales between the lateral line and base of dorsal, also 

 one more row between base of anal and lateral line; the rows of scales 

 in H. guppii above and in advance of anal are less strongly decurrent 

 and the interpolated rows are fewer. 



Habitat: Rio Tuyra Basin, Panama. 



25. Genus Hyphessobrycon Durbin. 



Hyphessobrycon Durbin, in Eigenmann, Bull. Mus. Comp. Zool., LII, 



1908, 100 (type Hemigrammus compressus Meek). 

 Dermatocheir Durbin, Ann. Carnegie Mus., 1909, 55 (type Dermatocheir 



catablepta Durbin). 



Body short, compressed, the back elevated; head short; premaxillary 

 teeth in 2 series; maxillary teeth, if present, crowded on the upper 

 anterior angle; lateral line incomplete; caudal fin naked; the lobes equal 

 or subequal. 



