1903.] NATURAL SCIENCES OF PHILADELPHIA. 527 



83. Acestrorhynchus " falcatus (Bloch). 



Salmo falcatus, Bloch, taf. 385. 



Xiphorhynclms falcatus Agassiz, Selecta Genera et Species Pise, 76, 1829; 

 Cuv. and Val., XXII, 337; Castelnau, 75 (Amazon). 



Xiphorhamphns falcatus Miiller and Troschel, Hor. Ichthyol, I, 17, 1845 

 (name only) ; id. in Schomburgk Reisen in Brit. Guiana, 635, 18-48 (Esse- 

 quibo, Pomeroon) ; Kner, Denkschr. Acad. Wiss. Wien, XVIII, 57, 1860 

 (Matto Grosso); Giinther, Cat. Fish. Brit Mus., V, 354, 1864; Eigenmann 

 and Eigenmann, Proc. U. S. Nat. Mus., XIV, 58. 



Xiphorhamphns ferox Giinther, Ann. and Mag. Nat. Hist., XII, 443, 1863 

 (Essequibo); Giinther, Cat. Fish. Brit. Mus., V, 355 (Essequibo); Bou- 

 lenger, Trans. Zool. Soc. Lond., XIV, Pt. II, 37, 1896 (Paraguay). 



The X. ferox of Giinther differs from falcatus chiefly in the length of 



the maxillary, also in the size of the eye, the scales, etc. Both species 



have been found in the Essequibo river. We have four specimens 



(33 and 49), ranging from 22 cm. to 27 cm., from the Rio Paraguay at 



Asimcion. There is no doubt that these specimens belong to the same 



species. Their measurements are as follows: 



27 cm. A. 24, Scales 107, Eye 6f, Snout [2f , Depth 3f , Max. 1 diam. 



beyond eve. 

 25 cm. A. 27, Scales 106, Eye 6, Snout 2|, Depth 3f, Max. 1 diam. 



beyond eye. 

 23 cm. A. 27, Scales 97, Eye 5i, Snout 24, Depth 34, Max. i diam. 



beyond eve. 

 22 cm. A. 27, Scales 103, Eye 54, Snout 2f , Depth 4, Max. f diam. 



beyond eye. 

 The measiu'ements nearly bridge the differences said to exist between 

 falcatus and ferox in the number of anal rays, the scales and length 

 of the maxillary. We have, therefore, placed ferox provisionally in 

 the synonymy of falcatus, of which it is probably the yoiuig. A speci- 

 men of X. falcatus in the collections of the Indiana University from 

 "Brazil," 22 cm., differs from our smallest specimen in the shape of 

 the mouth and the extent of the maxillary. The maxillary extends 

 for a distance equal to f diameters of the eye beyond its posterior 

 border. This difference is in part due to the greater length of the 

 maxillary, and also in part to the fact that it makes less of an angle 

 where it joins the premaxillary. 



In the absence of specimens from the Rio San Francisco the A', lacus- 

 tris of Reinhardt is kept distinct. It is unquestionably a local race of 

 falcatus, if it is not identical with it. 

 84. Acestrorhamplius ' hepsetus (Cuv.) Blanquillo. 



One specimen (15), Lagima at Asuncion. As this specimen differs 

 from the available figures of hepsetus, especially in the pectoral, and 

 may represent a distinct species, a description is added. 

 Head 3f ; depth 3^; D. 11; A. 30; scales 13-75-10. 



* New for Xiphorhijnchus Agassiz, preoccupied. 

 '' New for Hydrocyon hepsetus Cuv. 



