340 ACRONURID^. 



29. Acanthurus leucosternon. 



Acanthurus leucosternon, Benn. Proc. Zool. Soc. 1832, p. 183 ; Bkek. 



Batoe, iii. p. 237. 

 delisianus, Cuv.SfVal. x. p. 193; Gtier. Iconogr. Poiss. pi. 35. fig. 2. 



D-i^- A.,-^. V.1/5. 

 Scales very small, smooth. The height of the body is contained 

 once and four-fifths in the total length (the caudal fin not included). 

 The upper jaw with five truncated and lobate teeth on each side. 

 Caudal spine terminating posteriorly in a projecting process. The 

 upper profile of the snout is sub vertical and slightly concave. Caudal 

 fin emarginate. Blue : head black ; chest, and a ring encircling the 

 lower part of the mouth, white ; dorsal fin yeUow ; caudal with two 

 black crescents, one across the base, the other along the margin, 

 both united by the upper and lower black edges of the fin. 



Mamitius. Ceylon. Batoe. 

 «. Fine specimen. Ceylon. From Mr. Sibbald's Collection. — Type 

 of the species. 



30. Acanthurus achilles. 

 Shaw, Zool. iv. p. 383 ; ? Cut. 4- Val. x. p. 218. 



D.^. A. A V.1/5. Vert. 9/13. 



A large rhombic, naked, yellowish patch on the tail, including the 

 caudal spine. Anterior profile of the snout subvertical, nearly 

 straight. Four truncate and lobate teeth on each side of the upper 

 jaw. Brown : patch on the tail yellowish ; a narrow bluish line 

 along the base of the dorsal and anal fins ; a bluish ring across the 

 chin, from one angle of the mouth to the other ; subopercular mar- 

 gin and outer half of the ventrals bluish. Caudal fin with the base 

 deep brown, lighter across the middle ; a narrow brown crescent 

 between the light centre of the fin and the broad white margin. 



Sea of China. 

 a-h, c, d, e,f. Fine specimens. China. 

 g. Adult : skeleton. China. From the Haslar Collection. 



Valenciennes gives as the formula of the fins, D. ^» A. ^ ; but he 

 examined only a single dry specimen. 



The skeleton difiers so little from that of A. triostegns, that it will 

 be sufficient merely to give the measurements of some of its parts. 



lines. 



Length of the first vertebra 0^ 



of the second vertebra 1 



of the tenth vertebra 2 



of the twentieth vertebra 1| 



of the twenty-first vertebra 0| 



of the abdominal portion 14 



of the caudal portion 24 



of the twelfth neural 9 



of the first haemal 12 



of the first interneural 6^ 



of the first interhaemal 15 



