FISHES OF HAWAIIAN ISLANDS. 
383 
and Mid. Amer., n, 1687, 1898 (Honolulu); Steindachner, Denks. Ak. Wlss. Wien, LXX, 1900, 489 (Honolulu); 
Fowler, Proc. Ac. Nat. Sci. Phila. 1900, 513 (Sandwich Islands). 
Cfuetodon nudus Gray, Cat. Fish., Coll. Grono'w, 76, 1854, Mari Indico. 
Gonopterus mcerens Gray, Cat. Gronow, 77, 1854, India. 
Zanclus canescens, Jenkins, Bull. U. S. Fish Comm., XXII, 1902, (Sept. 23. 1903), 475 (Honolulu); Snyder, op. cit. (Jan. 19, 
1904), 533 (Honolulu; Puako Bay, Hawaii; Laysan Island). 
Family LXXV. ACANTHU RID^E. —Surgeon-fishes. 
Body oblong, compressed and usually elevated, covered with very small scales; lateral line con¬ 
tinuous; tail armed with one or more spines or bony plates; eye lateral, high up; preorbital very 
narrow and deep; nostrils double; mouth small, low; each jaw with a single series of narrow incisor¬ 
like teeth; vomer and palatines toothless; premax diaries somewhat movable but not protractile; 
maxillary short, closely united with the premaxillary; gill rakers obsolete; pseudobranchue large; gills 
4, a slit behind the fourth; gill-membranes attached to the isthmus, the openings thus restricted to 
the sides. A single dorsal fin, with strong spines, the spinous part of the fin shorter than the soft part; 
anal fin similar to soft dorsal; pectorals moderate; ventral fins present, thoracic, i, 5. Pelvic bones 
long, narrow, curved, closely connected, evident through the skin, as in Balwtidx. Pyloric cceca 
rather few; air-bladder large; intestinal canal long. Vertebrae 9 - 13=22. Posterior suborbital bones 
in close contact with the preopercle; post-temporal immovably united with the skull, apparently sim¬ 
ple, but really trifurcate with the interspaces tilled in with bone, the foramen not passing through it; 
interneural bones with transversely expanded buckler-like subcutaneous plates, which intervene 
between the spines and limit their motion forward; epipleurals developed from the ribs. Herbivorous 
fishes of the tropical seas, which undergo great changes with age, as do the Chxtodontidx , the young 
having often been described as distinct genera. 
a. Caudal peduncle armed with a single sharp, antrorse, lancet-like, movable spine; ventral i, 5. 
b. Teeth of jaws immovable. 
c. Dorsal with about 9 spines. Hepatus, p. 383 
cc. Dorsal with 4 or 5 spines.. Zcbrasoma, p. 395 
bb. Teeth of jaws movable; dorsal with 8 spines. Ctenochictus , p. 398 
aa. Caudal peduncle with 2 immovable bony plates, with keels or rigid spines; ventral rays I, 3. 
d. Teeth serrulate; adult with long horn above eyes. Acanthurus, p. 399 
dd. Teeth not serrulate; forehead without horns. Callicanthus , p. 403 
Genus 179. HEPATUS Gronow. 
This genus includes those Acantkuridx which have the tail armed with a sharp, antrorse, lancet-like, 
movable spine; strong, fixed, incisor teeth; ventral rays i, 5, and about 9 spines in the dorsal fin. 
The numerous species are found in all tropical seas. Herbivorous fishes, living about coral reefs; the 
adult protected by the murderous caudal spine, which grows larger with age. 
Rhombotidcs Klein, Historia Piscium, 37, 1740 (nonbinomial). 
Hepatus Gronow, Zodphyl., 113, 1763 (hepatus). 
Teuthis Linnaeus, Syst. Nat., 12th ed., 507, 1766 ( hejtatus; javus; after Hepatus Gronow). 
Harpurus (Forster) Gmelin, Syst. Nat., 1,1269,1788 (species “cauda utrique spina vel squama ossea falcata munite”). 
Aspisurus Lacepede. Hist. Nat. Poiss., IV, 556, 1802 ( sohar ). 
Theuthis Cuvier, Tab. El. Hist. Nat., 371, 1798. 
Theutis Cuvier, Regne Animal, 1st ed., II, 330, 1817 (restricted to Les Acanihures; allies of Hepatus hepatus). 
Tcuthi/s Swainson, altered orthography. 
Acronurus Gunther, Cat., in, 345, 1861 ( orbicularis; young fishes apparently scaleless). 
Rhombotides (Klein) Day, Fishes India, I, 202, 1876. 
Acanthurus , of authors generally, not of Forskal as here understood. 
a. Spine on caudal peduncle in a large ovoid cherry-red blotch becoming yellow in spirits . achillcs, p. 384 
aa. Spine on caudal peduncle not as above. 
b. Shoulder with a yellow or scarlet horizontal stripe margined with blackish running from gill-opening above pectoral, 
this becoming yellowish in spirits, merely blackish in young. olivaceus, p. 385 
bb. Shoulder not as above. 
c. Head with a white band from before spinous dorsal downward, across opercle, including margin of preo¬ 
percle . leucoparcius, p. 386 
cc. Head without white band. 
d. Side of body without longitudinal lines or cross-bands. 
e. No black on last rays and axils of dorsal and anal; body comparatively deep, depth 1.7 to 1.9 in length. 
