Zehrasoma and Paracanthurus — -RANDALL 
I have examined 167 specimens from the 
Philippines, East Indies, Gilbert Islands, 
Samoa Islands, Society Islands, and Mauri- 
tius, and all were brown. Jordan and Seale 
(1906: 356) had 50 specimens from Samoa 
and saw none yellow in color. Fowler (1928: 
274) recorded Z. flavescens from the Hawaiian 
Islands, Johnston Island, Samoa, Marcus Is- 
land, and Raiatea and described the species 
from preserved specimens as fuscous-black 
with fine grayish lines. Of his specimens only 
those from Samoa and Raiatea were of this 
color; the rest were pale yellowish. 
Only from Bikini Atoll in the northern 
Marshall Islands have I seen both yellow and 
brown specimens from the same area. Of 14 
specimens only one was yellow. Aoyagi (1943: 
204) reported both yellow and brown and 
intermediate forms from the Riu Kiu Islands, 
however, he mentioned that there was some 
geographical separation. R. R. Harry (1953: 
152) stated that he observed one yellow spec- 
imen underwater at Raroia Atoll in the Tua- 
motus but took only the dark form. Upon 
discussing this sight record with Harry, I 
learned that he was unaware of the solid 
bright yellow color of the young of Acan- 
thurus olivaceus Bloch and Schneider. He than 
stated that he could not be certain that the 
specimen he saw was Z. flavescens and not A . 
olivaceus. 
My efforts to distinguish the yellow Z. 
flavescens and the brown Z. scopas on other 
grounds than color met with the usual failure 
except for fin ray counts (Table 1) which 
provide a partial separation, the counts of Z. 
flavescens being higher. One might say that 
this meristic difference is due to the colder 
water of the northern part of Oceania to which 
the yellow "phase” seems to be restricted. 
However, the water of the Mariana Islands is 
as warm as the warmest areas of the Pacific 
(more specimens are needed from this region 
however, to be certain that the fin ray counts 
are really higher), and the fin ray counts of 
Z. scopas from the Society Islands, which are 
about as far south as the Hawaiian Islands 
407 
are north and have sea surface temperatures 
which are almost as cool as Hawaii (Hydro- 
graphic Office, 1944), show no increase (Ta- 
ble 1). Also Z. veliferum does not exhibit any 
obvious increase in ray counts in the Hawaiian 
Islands. 
In view of the available data, I do not 
believe that Z. flavescens and Z. scopas can be 
considered as color varieties of one poly- 
morphic species. If they were color varieties, 
at least an occasional brown specimen should 
have turned up in areas like the Hawaiian 
Islands, or yellow ones from the southern or 
western tropical Pacific or Indian Oceans. 
More important, one would not expect the 
fin ray counts of both phases to be different. 
Two other possibilities exist: the brown and 
yellow forms are full species or they are sub- 
species. My data are not yet sufficient to de- 
cide with assurance which is the case. At the 
present time I favor considering the two as 
species, although I may be placing too much 
emphasis on the single yellow specimen from 
Bikini with higher fin ray counts than brown 
specimens from the same atoll. This one yel- 
low specimen might have been carried there 
as a larva from a Z. flavescens area such as Wake 
Island. If this were true, the case for sub- 
species would be strengthened. 
The claim made by Aoyagi that yellow, 
brown, and intermediate forms occur in the 
Riu Kius is difficult to assess and should be 
checked. The intermediate forms were de- 
scribed as yellowish brown with minute spots. 
This is normal coloration for subadult and 
juvenile Z. scopas; thus this author might not 
have observed true intermediate forms at all. 
If the "geographical separation” which he 
mentioned is north-south within this island 
chain and true intermediate forms were found 
in a region of contact of the yellow and 
brown, the best explanation would be in 
terms of subspecies. 
I examined the type of Zebrasoma supra-alba 
Fowler from the Riu Kiu Islands at the Acad- 
emy of Natural Sciences of Philadelphia. The 
unique feature of the anterior part of the 
