ACRONURID.JJ. 325 



Fam. 30. ACRONURID^. 



Teuthyes, part., Cuv. Regne Anim. ; MiUl. Berl. Abhandl. 1844, p. 201. 

 Acanthuroidei, Sleek. Eiium. Spec. p. xxii. 



Body compressed, oblong or elevated, covered with minute scales. 

 Lateral line continuous ; tail generally armed with one or more bony 

 plates or spines, which are more developed with age, and frequently 

 absent in very young individuals. Eye lateral, of moderate size. 

 Mouth smaU ; a single series of more or less compressed, sometimes 

 denticulated, sometimes tapering incisors in each jaw ; palate smooth. 

 One dorsal fin, the spinous portion being the less developed ; anal 

 with two or three spines ; ventral fins thoracic. Pseudobranchiae well 

 develojjed ; air-bladder present, forked posteriorly. Intestines with 

 more or less numerous circumvolutions. Vertebrae ^J ^^ . 



Seas between the tropics. Herbivorous fishes. 



Synopsis of the Oenera. 



Ventral fin generally with five soft rays ; a single move- 

 able spine on each side of the tail ; scales minute, 1. Acanthurus, p. 325. 



A single moveable spine on each side of the tail ; scales 



none ; skin with vertical strife 2. Acronurus, p. 345. 



Ventral fin with five soft rays; a series of several 



keeled, bony laminaj on each side of the tail 3. Prionurus, p. 347. 



Ventral fin with three soft rays ; caudal laminae im- 

 moveable, generally two, rarely one or three 4. Naseus, p. 347. 



Caudal spine none (in an adult state) 5. Keris, p. 355. 



1, ACANTHURUS*. 



Acanthurus, Bl. Schn. p. 211. 



A single series of lobate incisors, which are sometimes moveable, 

 in the jaws. A moveable spine in a groove on each side of the tail. 

 Ventral fins composed of a spine and generally of five rays. One 

 dorsal fin, the spinous portion of which is less developed than the 

 soft ; anal spines three. Scales minute, ctenoid, sometimes spiny. 

 Branchiostegals five ; pseudobranchiae well developed ; aii'-bladder 

 large, forked posteriorly. Intestinal tract with several circumvolu- 

 tions ; five to seven pyloric appendages. Vertebrae ^-^. 



Herbivorous fishes from the tropical seas. 



* 1. Acanthurus flavo-guttatus, Kiffl. in Mus. Senck. i. p. 195. tab. 13. fig. 5. — 

 A. Ketlitzii, Cuv. ^ Val. x. p. 222. — Caroline Islands. The typical speci- 

 men is in the St. Petersburg Museum. 



2. bahianus, Castcln. Anim. nouv. Amer. Sud, Poiss. p. 24. pi. 11. fig. 1. — 



Baliia. 



3. brevis, Poey, Mem. Cub. ii. p. 207. — Cuba. 



4. tractus, Poey, Mem. Cub. ii. p. 208. — Cuba. 



