FISHES OF THE PHOENIX AND SAMOAN ISLANDS 157 



46. No white band or spot on posterior or lower angle of operculum. 

 60. Sides of body with a pale ground coloi', often tinged with dusky 

 purplish and crossed with five or six narrow blackish (dark 

 purplish in life) vertical bands, first from occiput through eye, 

 ending on lower edge of cheek ; second from first dorsal spine 

 to base of pectoral and continuing below a short distance in very 

 young specimens ; base of pectoral with a round black spot ; 

 third band from about between sixth and seventh dorsal spine 

 to above anus ; fourth band from fourth or fifth soft dorsal to 

 front of anal ; fifth band from about thirteenth or fourteenth 

 soft dorsal to middle third of anal ; last band or sixth in young 

 may be a ring around caudal peduncle or only a pair of dots 

 dorsally and ventrally on caudal peduncle ; across base of caudal 

 fin in very young specimens only is a black line and another 

 near tips of fin rays, both of which disappear by the time a 

 length of 30 mm. is reached ; peritoneum black ; dorsal rays 

 about IX, 23 ; anal III, 20 or 21 ; pectoral I, 13 or 14 ; teeth 12 to 

 14 + 16 to 18 ; gill rakers 5 or 6 + 14 to 16. 



Acanthurus triostegus (Linnaeus) 



6&. Sides of body (head and trunk) without five or six vertical blackish 



lines or narrow bars on a background of pale color. 



7a. Posterior third to half of rays of pectoral fin same color as 



anterior half to two-thirds of that fin. 



8ff. Caudal fin with a pale band posteriorly, becoming narrower on 



upper and lower lobes, then a diffuse brownish band grading 



into darker, followed by a submarginal black line that follows 



outer contour or caudal fin, color of basal three-fourths of 



caudal fin blackish, no liglit band inside black line in caudal 



fin ; ground color of body blackish ; a narrow pale area around 



spine on caudal peduncle ; margin of dorsal and anal fins with 



a white line posteriorly and at base cf rays of dorsal and anal 



fins a white line that expands posteriorly to include one-third 



of basal portion of last few rays ; outer margin of pelvics with 



white line, rest of fin black ; anus pale ; dorsal rays IX, 28 to 



31 ; anal III, 27 ; pectoral I, 15 or 16 ; gill rakers 5 -f 12 or 



13 ; teeth 8 or O-j- 10 to 12_Acanthuru3 rackliffei, new species 



8&. Color of caudal fin not as in 8a. 



9a. Head and trunk with about 11 sets of ne;irly longitudinal lines, 

 each set consisting of a blue line, bordered above and below 

 by a narrow black band, between each set a pale band (yel- 

 low or orange in life) ; band that passes through spine on 

 caudal peduncle ends at base of caudal fin rays, but set of 

 lines above and below this one turns at right angles on base 

 of caudal fin and ends dorsally and ventrally, followed 

 posteriorly by two transverse sets ; other sets of bands con- 

 tinue on dorsal fin for a short distance, above which are 

 several nearly parallel wavy pale streaks ; lowermost band 

 passes from moutli just below pectoral base to caudal fin 

 base, area below this band uniform pale or dusky ; anal fin 

 with margin white, then a narrow submarginal black line, 

 rest of fin dusky, base with a pale line ; pelvics black-edged ; 

 caudal fin lunate, mostly blackish, but with a crescent-shaped 

 pale line posteriorly; dorsal rays IX, 27 or 28; anal III, 26 



