FISHES OF THE PHOENIX AND SAMOAN ISLANDS 159 



obvious; pectoral dusky but paler than body, its 

 base color of body ; peritoneum black ; a black spot 

 at bases of last dorsal and last anal rays, more 

 evident in pale specimens 30 to 100 mm. but not so 

 obvious and iisually not distinguishable on black 

 specimens 100 mm. and larger ; dorsal rays IX, 24 

 or 25; anal rays III, 23 or 24; pectoral about I, 15; 

 teeth about 10 to 12-f 14 ; gill rakers 5 or 6+14 to IG ; 

 the smaller specimens 30 to 100 mm. have a lunate 

 caudal flu which becomes only concave at a length 

 of 120 mm. and longer ; specimens in pale phase of 

 color have blackish lips and outer edges of dorsal 

 and anal fins much darker than rest of body ; some 

 si^ecimens with caudal peduncle paler than body. 



Acanthurus elongatus (Lacepede) 



7&. Posterior third to half of pectoral fin pale or golden colored, 



sharply contrasting with dusky or blackish half to two-thirds 



of that fin. 



13(/. An oblong white band bordered with jet black extending from 



a little back of eye a distance equal to length of pectoral ; 



ground color of head and trunk blackish; pelvics, dorsal, 



and anal fins black ; posterior one-third to one-half of pectoral 



fin pale, upper edge of pectoral pale too ; caiidal fin a little 



paler than body but brownish black, with faded blackish 



spots in lobes of fin, middle area of caudal fin posteriorly 



white, but very edge of white area has a black line ; dorsal 



rays IX, 24; anal III, 23; pectoral I, 17, teeth about 18+20. 



Acanthurus olivaceus Bloch 



13&. No black-bordered white band extending a short distance 



back of eye, as In 13a. 



14fl. Posterior margin of caudal fin with a narrow white band, 



then a submarginal blackish line grading into dusky 



caudal fin ; beliind eye a jet-black band extending to over 



middle of length of pectoral fin ; a jet-black lanceolate 



line extending anteriorly, from spine on caudal peduncle, 



a distance about equal to length of pectoral fin ; ground 



color of head and trunk blackish, dorsal and anal fins as 



black as body near their bases but paler distally, margin of 



dorsal and anal fins with a narrow jet black band along 



llioir margins; posterior one-fourth to one-third of pectoral 



fin abruptly paler than blackish two-thirds to three-fourths 



of that fin; dorsal rays IX, 27; anal III, 24; pectoral I, 17; 



teeth 17+20 Acanthurus nigricans (Linnaeus) 



146. Posterior margin of caudal fin dusky or blackish, not white 

 and sharply contrasting with darker color of rest of flu; 

 ground color plain brownish or pale brownish ; area 

 around lower part of eye pale above and in front of 

 orbit; basal two-thirds of pectoral dusky to brownish, 

 the distal half to a third pale; pelvics du.sky, edges dark 

 brownish, central area of fin paler ; dorsal and anal fins 

 with about five or six alternating blacki.sh and pale 

 longitudinal bands along base of rays of dorsal, anal fin a 

 pale streak, brilliant bluish in life, rather indistinct in 

 alcoholic specimens; caudal fin at base a little lighter 



