234 BULLETIN 10 0, UNITED STATES NATIONAL MUSEUM 



Chaetodon nigricans Bonnaterre, Tabl. Ichth., 1789, p. 83, pi. 45, fig. 171 

 (Red Sea). 



Har-ptirus nigricans Forster, Fauna Indica, 1795, p. 15. 



Acanthus nigricanus Suckow, Naturg., vol. 4, 1799, p. 375. 



Acanthurus gahm Ruppell, Atlas Reise Nordl. Afrika, Fische, 1828, p. 58 

 (Djedda, Massauah). — Valenciennes, Hist. Nat. Poiss., vol. 10, 1835, p. 

 219 (Red Sea, Mauritius).— Gunther, Cat. Fish. Brit. Mus., vol. 3, 1861, 

 p. 338 (copied). — Klunzinger, Verli. zool. bot. Ges. Wien, vol, 21, 1871, 

 p. 506 (Red Sea). — GtJNTHER, Journ. Mus. Godeffroy, vol. 4, 1874, p. 113, 

 pi, 74 (Society Islands, Paumotu, Samoa, Hervey Islands, Kingsmills, 

 Gilbert Islands).— Day, Fishes of India, Suppl., 1888, p. 789; Fauna 

 Brit. India, vol. 2, 1889. p. 141.— Sauvage, Hist. Nat. Madagascar, Poiss., 

 1891, p. 338. — Steindacher, Abh. Senckenb. Naturf. Ges., vol. 25, 1900, 

 p. 426 (Ternate).— Weber, Siboga Exp., vol. .57, Fische. 1913, p. 318 

 (Saleyer).— Pellegrin, Bull. Soc. Zool. France, vol. 39, p. 227 (Di6go 

 Suarez, Madagascar). — Herre, Philippine Journ. Sci., vol. 34, No. 4, 

 Dec. 1927, p. 411, pi. 12, fig. 2 (Tablas, Bantayan, Samal, Basbas, Bungau, 

 Clarendon Bay). 



Acanthurics gahhm Ruppell, Neue Wirbelthiere, Fische, 1835, p. 131 (Red 

 Sea).— Bleeker, Act. Soc. Sci. Ind. N6erland., vol. 3. No. 4, 1857-58, pp. 

 3, 8; No. 5, 1857-58, p. 2 (Macassar). 



Acanthurus (Rhombotides) gahm Klunzinger, Fische Roth. Meer., 1884, p. 84. 



Acanthurus gahmoides Guichenot, Notes I. Reunion, vol. 2, 1862, p. 6 (25). 

 Reunion. 



Depth 1^ to 2; head 3^ to 3%, width IJ/^ to 1.^. Snout Ih; 

 eye 3% to 4, 2% to 3^ in snout, 1}^ to IH in interorbital; teeth 

 16 to 18 in each jaw; maxillary 4 to 4^ in head; interorbital 2% to 

 3K> convex. Gill rakers 7 + 14, short, feeble points. 



Scales with minute circuli; apical denticles 11 to 14, with 2 or 3 

 series of transverse basal elements. 



D. IX, 24 to 28, ninth spine 1% to 2 in head, fourteenth ray 1% 

 to V/s; A. Ill, 26 or 27, third spine 2K to 2}4, first ray 1% to lii; 

 caudal deeply lunate, with long slender points, 23^6 to 2^i in com- 

 bined head and body; least depth of caudal peduncle 2^ to 3 in 

 head; pectoral 1; ventral 2J4 to 3. 



Chocolate brown generally. Eyes dusky brown. Blackish postoc- 

 ular bar extends short distance behind shoulder. Groove of caudal 

 spine blackish, with black streak extending forward on side of tail, for 

 several times length of spine at least. Fins all deep brown, with dusky 

 tinge. Hind caudal edge narrowly whitish. Hind pectoral edge 

 rather broadly whitish or pale. Some examples, especially small 

 ones, show pale gray base. 



Red sea, Mauritius, India, East Indies, Melanesia, Micronesia, 

 Polynesia, Hawaii. 



19150. Batan Island. June 5, 1909. Length 210 mm. 



8709. Batan Island and Rapu Rapu Island. June 5, 1909. 



15492 to 15494. Butauanan Island. June 15, 1909. Length 185 to 242 mm. 



8557, 8558. Bolinao. May 10, 1909. Length 257 to 294 mm. 



