A canthurus — RANDALL 
269 
tical dusky band at base of caudal fin. Life colors 
unknown. 
DISCUSSION: The transformation of the aero- 
nurus larval form into the juvenile stage in- 
volves some striking morphological changes. 
Notable are the formation of scales from narrow 
vertical ridges on the body and a prolongation 
of the snout. The difference in relative length 
of the snout of the two small specimens should 
be kept in mind when comparing proportional 
measurements involving head length. 
A. chronixis is closely related to A. pyroferus, 
having a similar configuration, especially with 
respect to the produced snout, similar meristic 
data, and the same stomach structure. The young 
of both species appear to be the only ones of 
the genus with rounded caudal fins, and both 
develop strongly lunate fins as adults. A. chron- 
ixis differs from pyroferus principally in colora- 
tion; it lacks the broad pale terminal band of 
the caudal fin, the white line nearly encircling 
the mouth, and the large pale area on the 
pectoral fin. Also there are different markings 
on the shoulder region of the two species. The 
type locality of both species is the Caroline Is- 
lands. 
Fig. 2. A, Juvenile of Acanthurus chronixis ; stand- 
ard length 46.9 mm. B, Postacronurus of A. chronixis; 
standard length 34.5 mm. Both specimens from Ifaluk, 
Caroline Islands. Photo by W. Courtenay. 
Fig. 3. Juvenile of Acanthurus pyroferus Kittlitz 
from the Society Islands; standard length 43 mm. Re- 
produced from a 35 mm. Kodachrome transparency. 
Color in life bright yellow with blue markings on 
head. 
NOTES ON OTHER SPECIES 
Randall (195 6b: 197) cast some doubt on 
the statement of Kittlitz (1834) that the young 
of Acanthurus pyroferus are dirty yellow in 
color, by suggesting that this author might have 
confused the young of this species with A. 
olivaceus Bloch and Schneider. Recent collec- 
tions of A. pyroferus in the Society Islands (Fig. 
3 represents the smallest specimen taken) have 
revealed that Kittlitz was largely correct. The 
young are yellow in color, although bright yel- 
low. Kittlitz, of course, may have seen spec- 
imen^) transforming from juvenile to the dark 
brown adult coloration, at which time the prin- 
cipal color might be described as dirty yellow. 
The change-over in color in three specimens 
occurred at standard lengths of 88, 94, and 95 
mm. One from the Marquesas had nearly at- 
tained adult color patterns at a standard length 
of 98 mm. 
In addition to the bright yellow color, ju- 
veniles of A. pyroferus have a brilliant blue ring 
around the eye, a blue margin on the opercle, 
a blue ring nearly encircling the mouth, a small 
bright orange area just above the base of pectoral 
fin, and a narrow pale margin and thin, black 
submarginal line posteriorly on the median fins. 
This striking color pattern is precisely the same 
as that of the small angelfish Centropyge flavis- 
