242 Fretp Museum or Natura History — Zoéxocy, Vor. X. 
origin of dorsal slightly nearer adipose than tip of snout; adipose fin 
shorter than head, 4.8 to 5.5 in length of body; caudal fin deeply forked, 
the upper lobe the longer; anal fin without distinct spine, its origin 
behind origin of adipose; ventral fins inserted under posterior rays of 
dorsal; pectoral spine with hooks on both sides in young, becoming 
smoother with age, 1 to 1.23 in head. 
Color bluish above, pale silvery below. Young with numerous round 
specks or spots on head and side, which become fewer with age and wholly 
disappear in specimens of 200 mm. and moreinlength. Fins unmarked. 
We have 8 specimens of this species, ranging in length from 142 to 
300 mm. All are from the lower Rio Tuyra, some of them from below 
the head of tide water. 
This fish is probably not distinct from P. iires (Bloch) of which 
there are at hand numerous specimens from the Rio Atrato and Rio 
Magdalena. However, we do not find the dark spots, so characteristic 
in the young from the Rio Tuyra, present in the specimens from the 
more southern streams. The occipital process apparently is also slightly 
wider in the Rio Tuyra specimens. Our specimens may, therefore, 
be considered a variety of P. clarias with dark spots present in all except 
the adults. 
Habitat: Rio Tuyra Basin. 
3. Genus Pimelodella Eigenmann & Eigenmann. 
Pseudorhamdia (non Bleeker) Steindachner, Sitzb. K. Ak. Wiss. Wien, 
LXXIV, 1876, 604 (type Pimelodus lateristriga Miller & Troschel). 
Pimelodella Eigenmann & Eigenmann, Proc. Cal. Ac. Sci., 2nd. Ser., I, 
1888, 131 (type Pimelodus cristatus Miller & Troschel). 
This genus differs from Pimelodus in having a narrower and more 
spine-like humeral process and the fontanel extends farther back, 
notably past anterior margin of eye. Only a single species is found in 
the waters of Panama. 
3. Pimelodella chagresi (Steindachner). 
Pimelodus (Pseudorhamdia) chagresi Steindachner, Sitzb. K. Ak. Wiss. 
Wien, LX XIV, 1876, 584 (Rio Chagres and its tributaries). 
Pimelodella chagresi Eigenmann & Eigenmann, Proc. Cal. Ac. Sci., and. 
Ser., I, 1888, 134 (Rio Obispo), and Occ. Pap. Cal. Ac. Sci., I, 1890, 
160 (Rio Chagres and its tributaries). 
Head 3.8 to 4.7; depth 5.2 to 6.2; D. I, 6; A. 11 or 12. 
Body elongate, compressed, the dorsal region moderately elevated; 
head rather narrow; snout tapering, 2.3 to 2.7 in head; eye 3.85 to 4.6; 
