208 ACANTHOPTERYGII. 



total length. Eyes — diameter 1/3 of length of head, 1 J diameters from end of snout, and 1 apart. Profile over 

 snout concave. Teeth — six lobate incisors on each side of the upper jaw. Fins — dorsal very elevated, fourth 

 dorsal ray highest, and equal to from 1/2 to 1/3 of the length of the body : anal also elevated, but not so 

 much so as the dorsal, it begins under ninth dorsal ray. Scales — rudimentary, ctenoid. Lateral-line — present. 

 Colours — grayish, with nine vertical bands, having white edges, from the back to the abdomen. The 

 ocular band passes through the eye and to the base of the ventral fin ; the second band through the base of the 

 pectoral to the anus. Head sometimes with white spots. Dorsal with four curved blue or white bands, six on 

 the anal and four on the caudal. These bands being more or less continuations of those on the body but more 

 vertically curved. Caudal usually spotted with white or a light colour. 



Jerdon observes of this species " Grumbum, Tarn. rare. I have only seen a dried skin procured by W. 

 Elliot, Esq." A specimen in the Calcutta Museum from the Andamans is 8|- inches in length. One in the 

 British Museum 16 long and 14 high. 



Col. Playfair (Fish. Zanzibar, p. 57) observes of A. Desjardinii, " this may prove to be only the adult 

 state of Acanthurus velifer, Bloch." But as his two specimens of A. Desjardinii=Q\ and 7 inches respectively, 

 and the type in the British Museum only 5 inches, and these are the whole of those present, it is hardly a ten- 

 able conclusion that they are the adult form, when an A. velifer, 16 inches long, exists in the collection. 



Habitat. — From the Red Sea and East coast of Africa, through the seas of India to New Guinea. 



Genus, 2 — Naseus, Commer. 



Monoceros, Bl. Schn. ; Naso, Lacep. ; Aspisurus, (Lacep.) Riipp. ; Axinurus and Priodon, Cuv. and Val. ; 

 ? Keris, part Cuv. and Val. ; Callicanthus, Swainson. 



Branchiostegals four or five : pseudobranchim well developed. Body rather elevated and compresssd. Eyes 

 high up, anterior to which there is a bony prominence, frontal horn, or crest-lilce protuberance. Teeth in the jaws in 

 a single row mid sometimes having their edges serrated : palate edenhdous. A single dorsal fin having few spines 

 (4-6) and many rays. Anal with ttoo spines, its rays similar to those of the dorsal. Ventral with one spine and 

 three rays. Scales rudimentary in the form of roughnesses of the shin Wee shagreen. Free portion of the tail having 

 from 1 to 3 heeled bony plates on either side in the adidt, which are indistinct or even absent in young specimens. 

 Air-vessel large, posteriorly forked. Pyloric appendages few (5-8). 



These fishes are said to have a very convoluted intestinal tract and to be herbivorous. They appear to 

 be found in Ceylon and probably may be taken at the Andamans. 



Geographical distribution. — Red Sea, East coast of Africa, seas of India to Polynesia. 



SYNOPSIS OF SPECIES. 



1. Naseus tuberosus. D. 2^-fo") -A-- jtW Teeth smooth. Anterior surface of forehead prominent. 

 Gray, dorsal and anal fins banded, pectoral and caudal edged with white. Mauritius and Ceylon to Polynesia. 



2. Naseus brevirostris. D. jy 6 ^, A. -^s'-go. Teeth finely serrated. A horn from opposite lower portion 

 of eye. Gray, with short transverse spots on the hind portion of the body. Caudal with a light edge. Seas 

 of India to the Malay Archipelago and beyond. 



3. Naseus unicornis. D. -aytf-g-, A. -j-g-?-^ Teeth smooth. Forehead with a long horn from opposite 

 upper third of eye. Dorsal and anal fins with longitudinal bands : caudal yellowish. Red Sea, East coast ot 

 Africa, seas of India to Polynesia. 



1. Naseus tuberosus. 

 Naso tuberosus, Lacep. iii, p. Ill, t. vii, f. 3. 

 Acanthurus nasus, Shaw, Zool. v, p. 376, pi. 51. 

 Naseus tuber, Cuv. and Val. x, p. 290. 

 Naseus tuberosus, Giinther, Catal. iii, p. 353. 



B. v, D. rffc P. 18, V. 1/3, A. „?„> C. 16. 



Length of head 4| to 1/5, of caudal 5J to 1/6, height of body 1/3 to 3| in the total length. Eyes— 

 diameter 3| to 1/5 of the length of head, 2| to 3| diameters from end of snout, and 1| to 1£ apart. Anterior 

 profile of the snout convex, forming a crest-like prominence in the adult. Teeth — rather compressed, pointed, 

 and from 18 to 20 on either side of both jaws. Fins — in young specimens the dorsal spines appear to be 

 . comparatively longer than in adults : in one of the latter the length of the fourth spine equalled its distance from 

 the base of the first. Pectoral equals 3/4 of the length of the head. Caudal emarginate, but subject to great 

 variation, in some being almost truncated, whilst in others the 'outer rays are considerably produced. Free 

 portion of the tail with two strong sharp lancet-shaped spines, one behind the other on either side in the adult. 

 Colours — gray, becoming dull yellow along the abdomen and covered with small dark spots. Dorsal and anal 

 fins with a narrow dark base, external to which is a broad orange band, margined with black and externally 

 edged with white. Pectoral and caudal edged with white. 



Habitat. — From the Mauritius and Ceylon to Polynesia. 



