1. ACANTHTJEUS. 341 



G. Tail with a black trianf/le. 



31. Acanthurus triangulus. 

 Cuv. 8f Val. X. p. 189. 



Tail with a black triangle, whilst its borders are yellow, which 

 colour extends over the whole upper part of the back nearly to the 

 eye. One-half of the pectoral black ; operculum with a yellow band. 



This species is described by Valenciennes from an old drawing of 

 Vlaming, and has not been recognized. 



H. A blue spot below the dorsal Jin. 



32. Acanthurus fraterculus. 



Retiard, ii. no. 47 ; Valent. no. 413. 

 Acanthurus fraterculus, Cuv. 8f Val. x. p. 206. 



Body oblong, anterior profile convex. Caudal fin emarginate ; 

 the dorsal and anal fins are low anteriorly, elevated and pointed 

 posteriorly. Brown, with three oblique blue and red bands on the 

 side of the head, two of which descend to the eye, and the third to 

 the mouth ; a blue spot below the middle of the dorsal fin ; base of 

 the caudal spine black. 



East Indies. 



This species, figured by Renard, has not been recognized. 

 II. TJie soft portion of the ventral Jin not fully developed. 



33. Acanthurus hepatus. 



Valeiit. iii. p. 473. fig. 404. & p. 472. fig. 402 ; Seba, iii. 33. 3. 

 Teuthis hepatus, L. Si/sf. Nat. i. p. 507 ; L. Gm. Syst. Nat. i. p. 1362. 

 Acanthurus hepatus, Bl. Schn. p. 211 ; Cuv. ^ Val. x. p. 183. pi. 288 ; 



Bleek. Floris, p. 325. 

 theuthis, Lacep. iv. pp. 549, 553. 



^•xh- ^-li^- ^-1/3. Vert. 8/14. 



Scales minute, rough ; cheek with small, bony, star-like plates. 

 The height of the body is one-haK or two-fifths of the total length 

 (caudal not included). The upper jaw with five or six lobate 

 incisors on each side. Caudal spine without a prominent process 

 posteriorly. The upper profile of the snout rather convex. Bluish- 

 grey, with a large black mark nearly entirely covering the back, 

 commencing with a narrow band above the orbit, including a large 

 oval grey spot on the middle of the side, and terminating on the tail 

 in two black bands I'unning along the upper and lower edges of the 

 tail and of the caudal fin ; the space between these two bands is 

 yellow, triangular, the point of the triangle being in front of the 

 caudal spine. Base of the dorsal and anal fins grey ; pectoral black- 

 ish, with a crescent-shaped yellow spot at the free margin. 



From Mauritius to New Guinea. 

 a, h. Adult and half-gi'own. Amboyna. Purchased of Mr. Frank. 



