A canthurus— Randall 
271 
dorsal and anal fins colored like body except for 
narrow, pale bine margins and an orangisb-yel- 
low area at the base of these fins which is 
broader posteriorly; caudal fin colored like body 
basally, pale distally, these two regions separated 
by a broad area which appears salmon under- 
water, and is the best recognition mark of the 
hybrid (examined closely this colored area is 
reddish orange outwardly and orangish yellow 
inwardly, with lobes of orange extending into 
the yellow ) . 
The Makatea and Takapoto specimens have 
been deposited in the SNHM (48869 ), and the 
Takaroa hybrid at the USNM (169883) (two 
of the original hybrids are located at the USNM 
and the third at the Museum of Comparative 
Zoology at Harvard ) . 
Two specimens of Acanthurus nubilus 
(Fowler and Bean), previously known only 
from Celebes in the East Indies, were collected 
by spearing in Moorea, Society Islands, outside 
the barrier reef. This species seemed moderately 
common in this area at depths of about 70-130 
ft. Like A. thompsoni (Fowler), with which it 
was occasionally associated, it was frequently ob- 
served well off the bottom. 
When seen underwater, nubilus was predom- 
inantly light blue except for a white caudal fin 
and a region of yellow around the caudal spine. 
After spearing and removing the fish from the 
water, it was noted that the white tail had 
altered to dark gray, and the body was dark 
yellowish brown with numerous lengthwise blue 
lines (60 counted vertically from origin of anal 
fin on 158 mm. specimen, and 66 on 169' mm. 
specimen). The blue lines were about half the 
width of intermediate brown bands. The head 
and thorax were bright blue with numerous, 
close-set, round, dark yellowish-brown spots ( in 
diameter about one-third the diameter of pupil 
of eye). A broad, brownish-yellow area was 
visible around the caudal spine; the socket of 
the caudal spine was whitish, the sheath whitish 
medially, shading through yellow to black at 
edge. The dorsal and anal fins were bluish gray 
basally and greenish brown distally with nu- 
merous dark brown bands. The pectorals were 
hyaline with blackish rays and the pelvics pale 
blue with blackish rays. 
The following counts and proportional meas- 
urements were made on the specimens: D VII, 
27; A III, 23 and 24; P 16; anterior and poste- 
rior gill rakers 23 (one specimen only); caudal 
concavity 6.7, head length 4.5, depth 2 to 2.1 
— -all in standard length; longest dorsal ray equal 
to head length; eye 3 in head length. 
These two fish differ from the 153 mm. hoi- 
otype in the USNM in less body depth (1.8 
in holotype) and shorter head (head length of 
holotype 4.1). In view of the great similarity 
in other features such as color pattern, I regard 
the above differences in measurement as prob- 
ably- within the range of variability of the 
species. The specimens have been deposited in 
the SNHM. 
The acanthurids from collections of fishes 
made at islands in the Indian Ocean in 1957 by 
James E. Morrow and associates were loaned to 
the author from the Bingham Oceanographic 
Laboratory, Yale University. The following 
species were collected in the Maldives: Acan- 
thurus triostegus (Linnaeus), A . lineatus (Lin- 
naeus), A . gahhm (Forskal), A. leucosternon 
Bennett, A. nigrofuscus (Forskal), Ctenochaetus 
striatus (Quoy and Gaimard), and Zebrasoma 
veliferum ( Bloch ) . From the Seychelles the fol- 
lowing were taken: Acanthurus triostegus, A. 
lineatus, A. leucosternon, A . nigrofuscus, and A. 
tennenti Gunther. The collections were made 
with rotenone from inshore waters. 
Acanthurus leucosternon is as well represented 
in the collections as other surgeonfishes, which 
stands in opposition to the statement of Randall 
(1956^: 196) that the species does-. not appear 
to be common, a view based on the paucity of 
specimens in the United States. The new spec- 
imens are most welcome in providing material 
for additional fin ray counts ( Table 2 ) . 
A . leucosternon appears to be confined to the 
Indian Ocean and East Indies. The closely related 
A. achilles remains unrecorded from the Indian 
TABLE 2 
Fin-ray Counts of Specimens of 
Acanthurus leucosternon FROM THE INDIAN OCEAN 
DORSAL SOFT RAYS 
ANAL SOFT RAYS 
LOCALITY 
28 
29 
30 
31 
26 
27 28 
Maldive Is. 
1 
1 
1 
1 
Seychelie Is. 
3 
7 
1 
1 
7 3 
