400 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
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Xasonus Rafinesque, Anal. Nature, 83, 1815; substitute for Naso. 
Prioclon (Cuvier) Quoy & Gaimarcl, Voy. Uranie, Zool., 377, 1824 (annulatus). 
Naseus Cuvier, Regne Animal, 2d eel., II, 225, 1829 (fronticornis ). 
Priodonticlithys Bonaparte, Destrib. Metod. Anim. Vest., 34, 1S33 ( annulatus ). 
Keris Cuvier & Valenciennes, Hist. Nat. Poiss., X, 304, 1835 (anginosus) . 
a. Caudal spines gray; forehead with a rounded protuberance. 
b. Color nearly plain; I). v, 28 incipiens , p. ICO 
bb. Color usually mottled; D. vi, 27 brevirostris, p. 401 
aa. Caudal spines blue; forehead in adult with a long horn; D. vi, 30 unicornis, p. 402 
326. Acanthurus incipiens Jenkins. Fig. 175. 
Head 2.75 in length; depth 2.2; eye 3.4 in head; snout. 1.4; interorbital space 3; D. v, 28; A. it, 
27; P. 18. 
Body oblong-ovate, compressed, the greatest depth under third dorsal spine; head short; anterior 
profile from tip of snout to front of eye concave, a distinct prominence in front of eye at level of its 
Fig. 175 .— Acanthurus incipiens Jenkins; from the type. 
lower border, from which the profile is nearly straight to origin of dorsal; ventral outline strongly 
convex from tip of snout to base of ventrals; dorsal and ventral outlines from origin of dorsal and 
ventral fins to base of caudal peduncle each in a long low curve, most convex anteriorly; head short; 
snout blunt; mouth small, horizontal, below axis of body; jaws each with a single series of fine, sharp, 
close-set, finely serrulate canine teeth; a short-curved groove in front of eye below nostrils, its length 
2 in eye; gill-opening long and oblique, extending far anteriorly, the upper end at vertical of first 
dorsal spine; interorbital space not strongly convex, the median ridge low. Bod)' rough velvety; each 
side of caudal peduncle with 2 very low weak horny plates, without spines, the distance between 
them 1.5 to 2 in eye; first dorsal spine rather strong, moderately rough, its length 1.7 in head; other 
dorsal spines smoother and more slender, the fifth 2 in head; soft dorsal not high, the rays of about 
uniform length, the longest about 2.5 in head; anal spines rather short and slender, the second equal 
to diameter of orbit, soft anal similar to dorsal, equally high; caudal deeply emarginate, the free edge 
of the 2 lobes forming a broad angle; upper lobe of the caudal somewhat the longer, its length 
nearly equaling head; ventral spines moderate, reaching base of first anal spine, their length 2 in head ; 
pectoral short, its length a little less than snout. 
