Juvenile Tunas— SCHAEFER and MARR 
267 
FIG. 3. Photograph of juvenile Auxis thazard (Lacepede) 
including the finlets, and around the posterior 
end of the urostyle. Large chromatophores in 
the peritoneum show through the body wall 
along the upper half of the body cavity. None 
of the fins or finlets bears pigment spots, with 
the exception of the first dorsal. The first dor¬ 
sal bears a few scattered chromatophores, large¬ 
ly distributed along the spines. However, the 
first dorsal in general appearance is virtually 
colorless, as may be seen in Figure 4, especially 
as contrasted with Euthynnus or Neothunnus. 
With increasing size the local areas of pigmen¬ 
tation expand. In our largest specimens the 
head is well pigmented. The dorsal half of the 
body is uniformly dark. This dark area extends 
below the mid-line on the caudal peduncle. 
The chromatophores in the peritoneum are no 
longer visible through the thickened body wall, 
and the ventral surface is unpigmented. Even 
in our largest specimens none of the fins is 
heavily pigmented; the caudal is more pig¬ 
mented than the others. 
Juvenile Auxis are rounder in cross section 
than Euthynnus, being relatively less com¬ 
pressed laterally. The head length and length 
of the caudal region in Auxis are less in com¬ 
parison to the total length than is the case in 
Euthynnus. The maxillary in Auxis generally 
