128 CALIFORNIA ACADEMY OF SCIENCES. 



Pimelodus sehce Kuer, SB. Ak. Wien, xxvi, 417, fig. 19, 1857 (Mara- 



bitanos). 

 Silurus sapipoca (Natterer MS.) Kner, 1. c, 418. 

 Pimelodus louchercri Gtiuther, Cat. Fish. Brit. Mns. v, 123, 1864 



(Bahia). 

 Pimelodus (Rhamdia) qneleni ciiprea Steindachuer, SB. Ak. Wien, 



Ixxiv, 1876, Stlsswasserfische siidostl. Bras.iii, 65 (Juiz de Fora). 

 Pimelodus {Pha77idia) cutjaba^ Steindachnei; 1. c, 76, foot-note (Cuy- 



Habitat: Kio Plata, north to the Amazon. 



This species seems to be most abundant southward; 

 it is subject to many variations. It is very closely related 

 to Piraelodus sebai C. & V.; the only constant difference 

 is the length of the barbels. Heterobranchus sextentacu- 

 latus Ag. agrees better with quelen than with any other 

 known species. The plate of Pimelodus bahianus Castel- 

 nau probably represents one of the variations of quelen. 

 We give a description of the species, and then add the 

 variations with the localities. 



Width of body less than its depth, strongly compressed 

 towards the tail. Head flat above, the sides sometimes 

 making an angle, sometimes not; greatest width of head 

 1|-1^ in its length; width at the angles of the mouth 2 

 in head; head covered with (usually) thin skin, the sur- 

 face of the bones either smooth or striate. Fontanel as 

 in sebce. Occipital process extending about half way to 

 the dorsal spine; large pores distributed in definite re- 

 gions about the head. 



Eye 2|-2f in snout, 6-7 in head, 2^-2| in interocular 

 space. 



Maxillary barbels extending to the posterior third of 

 the adipose in young, much shorter in adult; mentals 

 not to pectoral, postmentals beyond base of pectoral. 



Mouth wide, terminal; teeth of the lower jaw as usual, 

 those of the upper jaw in a band of uniform depth which 

 is 6|-8 in its width. Gill-rakers sometimes simple, some- 

 times profusely branched, 2+10. 



