94 FISHES OF WESTERN SOUTH AMERICA 
15793, 1, 95 mm., La Merced, Allen, July, 1920. 
15870, 1, Puerto Melendez, Pongo de Manseriche, Allen, October, 1920, too small for certain de- 
termination. 
Near R. sebae, from which it differs most consistently in the barbel length, a 
character variable itself in some localities. Width of body less than depth, be- 
coming compressed strongly toward the tail; head flattened dorsally; occipital 
process reaching half way to dorsal spine; large pores occurring in patches on the 
head; in the young, maxillary barbels reaching the posterior third of the adipose, 
but shortened with age; mental barbels falling short of pectorals, post-mentals 
beyond the base of the pectorals. 
21. RHAMDIA SEBAE (Cuvier and Valenciennes) 
Pimelodus sebae Cuvier and Valenciennes, 1840, Hist. Nat. Poiss., XV, 169. 
Pimelodus (Rhamdia) sebae Steindachner, 1876, Sitzb. Kk. Akad. Wiss. Wien, LX-XIV, 68. 
Rhamdia sebae Kigenmann and Kigenmann, 1888, Proc. Cal. Acad. Sei., (2), I, 126; 
Yigenmann and Kigenmann, 1890, Oce. Papers Cal. Acad. Scei., I, 123; 
Fowler, 1914, Proc. Acad. Nat. Sci. Phila., LX VI, 258; 
Fowler, 1915, Proc. Acad. Nat. Sci. Phila., LXVIT, 209; 
Fowler, 1939 (1940), Proc. Acad. Nat. Sci. Phila., XCI, 222, twelve, 120-214 mm., Conta- 
mana. 
Magdalena basin to that of Rio Janeiro; throughout the Amazon 
22. RHAMDIA MOUNSEYI Regan 
Rhamdia mounseyt Regan, 1913, Ann. Mag. Nat. Hist., (8), XII, 281, seven, 75-135 mm., Rio 
Ucayali. 
Known only from the types from an unnamed locality on the Rio Ucayali. 
23. RHAMDIA BATHYURUS (Cope) 
Pimelodus bathyurus Cope, 1878, Proc. Amer. Phil. Soc., XVII, 674, Peruvian Amazon. 
Rhamdia bathyurus Eigenmann and Eigenmann, 1888, Proc. Cak. Acad. Sci., (2), I, 124, 
Rio Maranon; 
EFigenmann and Higenmann, 1890, Oce. Papers. Cal. Acad. Sei., I, 122; 
Zigenmann, 1910, Rept. Princeton Univ. Exped. Patagonia, IIT, 385. 
Kknown only from the Cope specimens from the Maranon. 
24. RHAMDIA HUMILIS (Giinther) 
Pimelodus humilis Giinther, 1864, Cat. Fish. Brit. Mus., V, 129, Venezuela. 
Rhamdia humilis Eigenmann and Eigenmann, 1888, Proc. Cal. Acad. Sei., (2), I, 126; 
Eigenmann and Higenmann, 1890, Occ. Papers Cal. Acad. Sei., I, 127; 
Eigenmann, 1910, Rept. Princeton Univ. Exped. Patagonia, III, 385. 
Venezuela to the Maranon 
