160 BULLETIN 18 0, UNITED STATES NATIONAL MUSEUTM 



than peduncle, central area posteriorly blackish, rear 

 margin of caudal fin blackish (above color description is 

 of specimens 165 and 175 mm. long). In a specimen 44 

 mm. long caudal fin at base abruptly paler than grayish 

 body, distal half of caudal fin blackish ; longitudinal bars 

 in dorsal and anal fins barely visible, but margins of 

 these fins more blackish than basal two-thirds; longitudi- 

 nal stripes lacking in dorsal and anal of 425-mm. speci- 

 men, but at their bases a pale streak, blue in life. This 

 large specimen was dark blue-green above when alive and 

 paler below, in alcohol plain grayish ; pectorals as in 

 smaller specimens. Dorsal rays IX, 25 to 27 ; anal III, 

 24 or 25; pectoral I, 16; teeth about 15 or 16+16. 



Acanthurus fulig'inosus (Lesson) 

 36. Dorsal spines IV or V. 



15a. Ground color blackish or dark brown, with five or six pale trans- 

 verse bands and parallel faint blackish lines, first band from 

 just in front of dorsal fin through rear of orbit to base of pelvics, 

 second from below spinous dorsal fin under pectoral to origin of 

 anal, third, fourth, and fifth from dorsal to anal, sixth from dorsal 

 just in front of caudal spine to anal fin ; dorsal and anal fins with 

 transverse pale lines posteriorly; head in front of eye with numer- 

 ous small pale spots; peritoneum with many black pigment cells; 

 dorsal rays about IV, 30 to 32; anal about III, 24; pectoral 



about 1, 14; teeth 14+16 to 18 Zebrasoma velifenim (Bloch) 



156. Ground color blackish or yellowish, with transverse bands ; when 

 ground color is blackish caudal spine is whitish, trunk with 

 obscure wavy longitudinal bluish or grayish lines ; pectoral plain 

 pale, its upper edge with a black margin ; snout somewhat pro- 

 duced but not so long as in Zi. rostratum, pelvics, dorsal, caudal, 

 and anal fins plain black ; a short blue streak or pale band just 

 above and extending behind pectoral, sometimes distinct and 

 often not apparent ; iris usually golden, yellow, or grayish ; yellow 



phase not found here Zebrasoma flavescens (Bennett) 



16. Tail armed with two immovable keeled bony bucklers or rigid spines, these 



often obscure in small specimens ; teeth not crenulate at tips, as in la, 



but small and pointed, somewhat incisorlike ; dorsal spines VI or VII. 



16a. Caudal peduncle with two white areas around spines on caudal peduncle, 



meeting their fellows below, but absent on specimens of 55 to GO nam. ; 



ground color blackish; lips pale (yellow in life); vertical pale bar 



at rear of mouth, curving to front of eye; pelvic rays I, 2 or 3; very 



margin of soft dorsal with white line, then a black submarginal line, 



followed below by a white band, basal half of fin black; anal fin 



blackish with a marginal white line; rear margin of caudal flu white, 



rest of fin blackish ; pectoral blackish except tips are paler ; pelvic8 



blackish ; color of 55 to 60 mm. specimens about same as those over 



100 mm. in length, except yellow mark from mouth to eye absent ; 



no brown spots on sides of body as in young of Naso unicornis; dorsal 



rays VI or VII, 27 to 29; anal rays II, 29 or 30; pectoral I, 16 or 17; 



teeth about 25 to 27+21 to 23 Naso lituratus (Bloch) 



166. Caudal peduncle without white areas around spines ; no pale streak from 

 mouth to eye. 

 17a. Ground color brownish black, sides with small rounded spots of deep 

 violet-blue (blackish in alcohol), belly paler; lips blue; a streak 



