200 BULLETIN" 10 0, UNITED STATES NATIONAL MUSEUM 



protractile. Jaws with uniserial incisorlike teeth, rarely setiform. 

 Palate edentulous. Nostrils double, open close before eyes. Preoc- 

 ular groove present. Gill opening lateral. Gill rakers obsolete. 

 Pseudobranchiae large. Au- vessel large, bifurcated behind. Pyloric 

 appendages rather few. Intestine long. Vertebrae 21 to 2.3 ( = 9 or 

 8 + 12 to 14). Scales very small, firmly attached. Lateral line con- 

 tinuous to caudal base. Dorsal single, with strong spines and soft 

 fin usually larger than spinous. Anal like soft dorsal. Pectoral 

 moderate. Ventrals present, usually wdth spine and 5 rays. 



Herbivorous tropical fishes, many dark though often with some 

 brilliance, others notable for their contrast or deep bodies. All are 

 dangerous to handle, as by lashing the tail from side to side they are 

 able to inflict severe or dangerous wounds on the incautious by means 

 of the dreaded caudal spine. Fossils have been associated v>ith these 

 fishes as Aulorliamiihus De Zigno and Apostasis Kramberger, both 

 without caudal armature, the latter with a serrated opercle. 



ANALYSIS OF THE GENERA 



a}. Hepatinae. Tail armed with very sharp, antrorse, erectile, lancetlike spine, 

 fitting in a groove. 

 hK Teeth movable, rather long, bristlelike and expanded at tips; dorsal spines 



8 or 9 Ctenochaetus 



¥. Teeth immovable, lobate, broad, spines 6 to 10. 



fi. Ventral with -3 soft rays Paracanthurus 



c^. Ventral witli 5 soft rays. 



fP. Body oblong ovate to moderately ovate; dorsal spines 6 to 10; soft 



dorsal and anal not elevated in front; caudal usually lunate. Hepatus 



d^. Body deep, subrhomboid; dorsal spines 4 or 5; soft dorsal and anal 



high anteriorly; caudal truncate Zebrasoma 



a^. Nasinae. Tail armed with firmly immovable bony bucklers, each keeled or 

 with rigid spine. 



e'. Caudal bucklers 2 Naso 



e^. Caudal bucklers more than 2 Prionurus 



Genus CTENOCHAETUS Gill 



Ctenochaetus Gill, Proc. U. S. Nat. Mus., vol. 7, 1884 (1885), p. 279. Type 

 Acanthurus strigosus Bennett, orthotypic. 



Teeth long, slender, movable, bristlelike, with expanded tips strongly 

 serrulated. Dorsal spines 8 or 9. Coloration dark or sombre. 



CTENOCHAETUS STRIGOSUS (Bennett) 



Acanthurus strigosus Bennett, Zool. Journ., vol. 4, 1828, p. 41. Hawaiian 

 Islands. — Valenciennes, Hist. Nat. Poiss., vol. 10, 1835, p. 243 (New 

 Guinea). — Bleeker, Nat. Tijds. Nederland. Indie, vol. 4, 1853, p. 264 

 (Cauer); vol. 6, 1854, p. 313 (Larantuka, Florcs Island); vol. 8, 1855, p. 

 296 (Ternate), p. 306 (Batoe Island); vol. 9, 1855, p. 106 (Sabu, Halma- 

 heira), p. 234 (Manado, Celebes); vol. 10, 1856, p. 360 (Ternate); vol. 11, 

 1856, p. 81 (Malong, Java), p. 95 (Banda); vol. 12, 1856, p. 230 (Batu), p. 

 293 (Boleling, Bali); vol. 13, 1857, p. 372 (Sangi), p. 478 (Karangbollong); 



