1915.] NATURAL SCIENCES OF PHILADELPHIA. 213 



does not seem likely to be the young of that species. From R. riojce 

 it differs principally in the slightly protruding mandible, reversed 

 width of the internasal areas, the slightly longer adipose fin, and 

 the coloration. 



(Named for Prof. James Orton, who made collections in Peru 

 many years ago.) 



Rhamdia sapo (Valenciennes). 



Rio Jacuhy and Sao Joao to Rio Negro and Chapada, Brazil. 



Ehamdia brachyptera (Cope). 



Pimelodus (Rhamdia) brachypterus Cope, Trans. Amer. Philos. Soc, (3) 

 XIII, 1866, p. 404. Orizaba, Mexico. 



No. 16,471, A. N. S. P., type of P. (R.) brachypterus Cope. F. 

 Sumichrast. Orizaba, Mexico. Regan says,'* "the original descrip- 

 tion of P. brachypterus Cope, from Orizaba, is insufficient, but Fowler's 

 redescription of the type shows that this species is probably not 

 distinct from P. guatemalensis." However, according to Regan's 

 key, it cannot fall with any of the species he includes under his first 

 division with R. guatemalensis. It is likely somewhat near R. 

 managuensis, though the occipital process extends only one-fourth 

 the space from its base to the dorsal origin, and the infcerorbital 

 width is 2| in the head. 



Rhamdella bathyurus (Cope). 



Pimelodus bathyurus Cope, Proc. Amer. Philo.s. Soc, XVII, 1878, p. 674. Peru- 

 vian Amazon. 



Nos. 21,437 and 38, A. N. S. P., cotypes of P. bathyurus Cope. 

 Peruvian Amazon. J. Orton. Presented by E. D. Cope. This 

 species differs from Rhamdella parryi and R. minuta in coloration. 

 Rhamdella nicaraguensis (Gunther). 



One from Nicaragua (J. F. Bransford). Regan figures this species,^ 

 but the barbels are shown as not quite reaching opposite dorsal origin. 

 He says they extend to the origin of the adipose fin, according to 

 Gunther, and that "both barbels are now broken off in the type, the 

 longest reaching the middle of the dorsal." My example shows the 

 maxillary barbels reaching a little beyond ends of depressed ventrals. 



Rhamdella straminea Cope. 



Rhnmdella straminea Cope, Proc. Amer. Philos. Soc, XXXIII, 1894, p. 93, 

 PI. 8, fig. 10. Rio Jacuhy, Brazil. 



Nos. 21,581 to 84, and 21,604, A. N. S. P., cotypes. Rio Jacuhy, 

 Brazil. H. H. Smith. Presented by E. D. Cope. No. 23,216, 

 without data, is also identical (likely with the same data?). 



* Biol. Cent. Am. Pise, 1906-8, p. 128. 



* L.c, p. 131, PL 20, fig. 2. 



