402 
PACIFIC SCIENCE, Vol. IX, October, 1955 
with 15 upper and 17 lower teeth; 179 mm. 
specimen with 18 upper and 20 lower teeth. 
Longest soft dorsal ray 3 to 3-1 in standard 
length; fourth dorsal spine 4.5 to 5.9 in 
standard length; body depth 1.7 to 1.9 in 
standard length; no patch of setae on side of 
body anterior to caudal spine. All counts and 
measurements are based on two specimens. 
Color (in alcohol) brown with numerous 
white spots on head, body, dorsal and anal 
fins, base of pectoral fin, and very faintly on 
caudal fin (these spots tend to be round on 
fins, head, and dorsal part of body, but elon- 
gate elsewhere on the body) ; caudal fin pale. 
Cuvier and Valenciennes (1835: 256) stated 
that the caudal fin was yellow. Sauvage (1891: 
344) (after Lienard) described the spots on 
this fish as blue. 
Z. gemmatum is known only from the island 
of Mauritius and possibly Madagascar. 
Zebrasoma xanthurum (Blyth) 
Fig. 1 c; Fig. 5 
Acanthurus xanthurus Blyth in Kelaart (1852: 
appendix p. 50) (Ceylon); Gunther (1861: 
343) ; Playfair in Playfair and Gunther 
(1866: 57, pi. 8, fig. 4) (Aden); Klunzinger 
(1871: 504) (Red Sea); Day (1876: 207). 
Acanthurus ( Harpurus ) xanthurus Klunzinger 
(1884: 85). 
Zebrasoma xanthurum Fowler and Bean (1929: 
262). 
Dorsal rays V, 24 or 25; anal rays III, 19 or 
20; pectoral rays 15; gill rakers (from one 
specimen): anterior 11, posterior 13; upper 
teeth 18 to 20; lower teeth 22. 
Longest soft dorsal ray 3.4 to 3.7 in stand- 
ard length; fifth dorsal spine 3-9 to 4.1 in 
standard length; body depth 1.7 to 1.85 in 
standard length; an oval, velvety patch on 
side of body anterior to caudal spine. All 
measurement and meristic data except gill 
raker counts based on seven specimens, 120 
to 181 mm. from the Red Sea. 
Color (in alcohol) dark gray to black with 
small spots on head, nape, and chest (these 
spots pale on two of the specimens and dark 
on the others); entire caudal fin abruptly 
yellowish white just posterior to caudal spine; 
dorsal, anal, and pelvic fins dark gray; pectoral 
fin with basal two-thirds dark gray, outer one- 
third pale. 
Blyth (in Kelaart, 1882: appendix p. 50) 
described the color in life from a 7.5 inch 
specimen as ". . . wholly black with bright 
golden-yellow tail, and a tinge of the same 
upon the pectorals.” 
Fig. 5. Zebrasoma xanthurum (Blyth), (after Playfair, 
1866). 
This species is difficult to separate from 
Z. scopas and Z. flavescens on any basis other 
than color. The snout is slightly less pro- 
duced in Z. xanthurum and, for a comparable 
size, the velvet like area on the side much 
less developed. It seems likely that Z. xan- 
thurum attains a larger size. Four of the seven 
specimens from the Red Sea range from 145 
to 181 mm. in standard length. The largest 
Z. scopas I have seen is 149 mm. in standard 
length (from the Society Islands). Of over 100 
adult specimens in the United States National 
Museum from the Philippines and East In- 
dies, the largest is 145 mm. and only nine 
exceed 115 mm. The largest of many Z. flav- 
escens examined by me is a Hawaiian specimen 
149 mm. in length. 
Zebrasoma xanthurum is thus far reported 
only from Ceylon, the Gulf of Aden, and the 
Red Sea. 
