268 
PACIFIC SCIENCE, Vol. XIV, July I960 
Fig. 1. Holotype of Acanthurus chronixis from Kapingamarangi, Caroline Islands; standard length 211 mm. 
spines, A. sohal (Forskal) , A. pyroferus Kittlitz, 
and A. chronixis. The young of sohal is known 
(Randall, 1956b: fig. 1), and the young of 
pyroferus is described later in this paper. Al- 
though a series of specimens is lacking to link 
the two small ones from Ifaluk to the holotype, 
it seems likely that they represent the young of 
A. chronixis. There are meristic differences, 
however, that arouse some suspicion. The two 
small specimens have 15 pectoral rays and 27 
or 28 soft dorsal rays, as opposed to 17 pectoral 
rays and 26 soft dorsal rays for the holotype. 
The possibility that these two specimens are 
the young of a species as yet undescribed cannot 
be discounted. For this reason they are not 
designated as paratypes of chronixis. They are 
deposited in the Stanford Natural History Mu- 
seum (SNHM) under the number 52105. Their 
description follows (data for the transforming 
specimen in parentheses). 
Dorsal rays VIII, 27 (28); anal rays III, 25 
(25); pectoral rays, 15 (15); upper teeth, 12 
( 16, the two medial ones large and like adult 
teeth) ; lower teeth, 12 (18, a single large medial 
one ) . 
Depth of body 1.78 (1.64), head length 3.21 
(2.98), snout length 4.74 (5.95), length of 
pectoral fin 2.59 (2.63), length of pelvic fin 
3.72 (4.10), snout to origin of dorsal fin 2.06 
(2.33), snout to anus 2.18 (2.01), length of 
dorsal fin base 1.40 (1.41), length of anal fin 
base 1.95 (1.89)— -all in standard length. Great- 
est diameter of eye 2.44 (2.70), width of body 
2.00 (2.19), width of interorbital space 2.86 
(3.14) , postorbital length of head 3.74 (4.46), 
least depth of caudal peduncle 2.70 (2.76), 
length of caudal peduncle 4.30 (4.92), length 
of caudal peduncle spine 6.95 (7.26), length of 
pelvic spine 1.85 (2.70), length of first dorsal 
spine 5.40 (4.83), length of second dorsal spine 
2.61 (2.32), length of third dorsal spine 1.87 
(2.15) , length of eighth dorsal spine 1.23 
(1.84), length of first dorsal ray 1.20 ( 1.76), 
length of first anal spine 5.21 (5.80), length of 
second anal spine 2.66 (2.83), length of third 
anal spine 1.72 (2.07), length of first anal ray 
1.46 (1.90), width of mouth 3.56 (3.87) — -all 
in head length. Caudal fin markedly rounded. 
Color in alcohol of juvenile light brown with 
numerous faint pale spots on body, some con- 
fluent dorsally to form short vertical or diag- 
onal pale bars; median fins with dusky mem- 
branes, the dorsal and anal with rows of pale 
spots and the caudal with a narrow pale margin 
and a faint spotting in middle portion of fin; 
edge of upper portion of opercle dusky. Color 
of postacronurus uniform light tan with a ver- 
