A cant hums — Randall 
273 
by Smith from Aldabra: C. striatus, C. strigosus 
(Bennett), and CtenochaeUis sp. (the latter 
species was left undesignated pending the pub- 
lication of the revision of the genus). He pro- 
vided information on the latter species in a 
letter enabling me to identify it as C. cyanogut- 
tatus Randall. His specimen is 9 in. in length 
and was described as having "light blue spots 
all over in life. 5 ’ This is the first record of 
cyanoguttatus west of the Gilbert Islands, al- 
though the blue-spotted Acanthurus ctenodon 
Var .b of Playfair (1866: 57) from Zanzibar is 
probably also C. cyanoguttatus. 
After the revision of Ctenochaetus was pub- 
lished (Randall, 1955 d) , a large specimen of 
C. cyanoguttatus from Cocos Island was found 
at the USNM — probably one of the four spec- 
imens of Snodgrass and Heller (1904) orig- 
inally cataloged at the SNHM. As mentioned in 
the revision (p. 161 ) , no trace of blue spots 
could be found on the one Cocos Island spec- 
imen seen at Stanford. The National Museum 
specimen, however, possesses pale bluish spots 
on the side beneath the pectoral fins which are 
closely applied to the body. The cover provided 
by these fins probably prevented the fading of 
the spots at this location. 
Three specimens of C. cyanoguttatus , 212, 
202, and 120 mm. in standard length, were col- 
lected by spearing at Ua Pou in the Marquesas 
Islands. Numerous small, bright blue spots 
covered the head, body, and pectoral fins, those 
posteriorly on the body being smaller. A pale 
blue band was evident at the base of the dorsal 
and anal fins. These fins were banded alternately 
with pale blue and dark yellowish brown. The 
iris was dark blue. Many individuals under- 
water displayed whitish lips and a whitish caudal 
fin. The caudal may also be brown with length- 
wise blue streaks. This species was not seen in 
the Society Islands or Tuamotus but proved to 
be abundant at the three islands visited in the 
Marquesas, Ua Pou, Nuku Hiva, and Eiao. On 
the two occasions when C. cyanoguttatus was 
observed in the Gilbert Islands, it occurred in 
schools. It was not observed to school in the 
Marquesas. 
C. striatus, probably the most abundant reef 
fish of its size in the Society Islands, was never 
seen in the Marquesas, although much effort 
was expended to locate it there. The specimen 
reported by Fowler (1938: 76) as C. strigosus 
from Ua Pou and said to have blue lines on the 
body was examined at the Academy of Natural 
Sciences of Philadelphia. It is C. cyanoguttatus, 
and blue spots, not lines, are still evident on 
the body. 
When the two larger specimens of C. cyano- 
guttatus were collected by the author, difficulty 
was experienced in deciding whether they should 
be labelled as C. cyanoguttatus or C. magnus 
Randall. They were more like magnus in gen- 
eral appearance, with greater depth, convex pro- 
file, and scales in very irregular rows. There 
were, however, predominantly four denticula- 
tions on the expanded tips of the upper teeth 
as is seen on teeth of cyanoguttatus and not 
three, a number which was presumed to be 
diagnostic for magnus. Also the bands in the 
dorsal and anal fins persisted in preservative 
(these are not visible on the preserved spec- 
imens of magnus ). Leonard P. Schultz kindly 
loaned the types of cyanoguttatus (170.5 mm.) 
and magnus (225 mm.) from the USNM in 
order that they might be compared with the two 
large and one small Marquesan specimens. It 
was noted that some of the upper teeth of the 
holotype of magnus bear four instead of three 
denticulations. It now seems that the differences 
between these two forms are principally ones 
of age, and magnus should be referred to the 
synonymy of cyanoguttatus. 
Meristic data of the three Marquesan speci- 
mens of cyanoguttatus are given in Table 4. 
Randall (1955 h: 189) collected a 35 mm. 
specimen of Ctenochaetus from the Gilbert Is- 
lands which was not identified to species. It 
was brown with a bright yellow caudal peduncle 
and caudal fin. The specimen is shown in Figure 
TABLE 4 
Counts from Specimens of Ctenochaetus 
cyanoguttatus from the Marquesas Islands 
standard 
length 
(mm.) 
NUMBER OF TEETH 
NUMBER OF 
SOFT RAYS 
Upper 
Lower 
Dorsal 
Anal 
120 
41 
54 
27 
24 
202 
46 
65 
26 
24 
212 
42 
67 
27 
24 
