348 ACRONITRID^. 



Naso, Lac^j. iii. p. 106. 



Aspisurus, (Lacep.) JRiipp. Atl. Fische, p. 60. 



Naseiis, Axinm-us, et Priodon, Cuv. lif Val. x. pp. 257, 299, 302. 



A single series of slightly compressed incisors, which are some- 

 times denticulated, in the jaws. Tail with two (rarely one or three) 

 bony plates, which are very distinct and sharply keeled in adult, 

 indistinct or entirely absent in immature and young specimens. 

 Head sometimes with a bony horn- or crest-Hke prominence. Yen- 

 tral fins composed of one spine and three rays. One dorsal fin, the 

 spinous portion of which is much less developed than the soft, and com- 

 posed of four to six spines ; anal spines two. Scales minute, rough, 

 forming a sort of shagreen covering. Branchiostegals four or five ; 

 pseudobranchise well developed ; air-bladder large, forked posteriorly. 

 Intestinal tract with many circumvolutions; five to eight pyloric 

 appendages. 



Herbivorous fishes inhabiting the tropical seas from the eastern 

 coasts of Africa to Polynesia. 



* Forehead with a more or less elongate conical horn-like protuberance 

 in adidt specimens. 



1. Naseus unicornis. 



Monoceros piscis, Willughby, p. 150. t. 0. 4. 



minor, Willughhy, p. 216. 



Chsetodon, sp., Hasselq. Iter Palcest. p. 332. no. 71. 



unicornis, Forsk. p. 63, and Icon. tab. 23 ; L. Gm. i. p. 1268. 



Monoceros raii, Bl. Schn. p. 181. 



biaculeatus, Bl. Schn. p. 180. tab. 42. 



Naso fronticomis, Lacep. iii. pp. 105, 106. pi. 7. fig. 2. 



Acanthurus unicornis, Shaiv, Zovl. iv. p. 374. pi. 50. 



Aspinirus imieomis, It'dpp. Atl. Fische, p. 60. 



Naseus fronticornis, (Commers.) Cuv. Sr Val. x. p. 259; Faun. Jnpqn. 

 Poiss. p. 129. pi. 69 ; Richards. Ichth. Chin. p. 244 ; Bleek. Batoe, 

 iii. p. 238 ; Cm. Rk/ne Anim. Bl. Poiss. -pi. 72. fig. 2. 



longicornis, Cuv. in Guer. Iconogr. Poiss. pi. 35. fig. 3. 



Harpurus monoceros, Forst. Descript. Anim. ed. Lichi. p. 219. 



Acronm-us segyptius, Gronov. Syst. ed. Gray, p. lOl.f 



corniger, Gronov. Syst. ed. Gray, p. 192. 



D-(Si- A.,,:^. Ca.c.pylor.7-8. Vert. 9/12. 



Forehead produced into a horn-like protuberance, longer or 

 shorter according to age, horizontal, and on a level with the upper 

 half of the orbit. Snout produced beyond the tip of the horn (some- 

 times the horn is a little longer) ; the length of its upper profile, 

 taken from the base of the horn, is more than twice the distance of 



noiratre sur le dos, moins fonc6e sur le ventre et presque noire aux 

 nageoires. Sa caudale est si l^gerement echancree qu'eUe semble carree. 



D. — , A. —."—Mauritius. 



30' 30 



t Gronow gave this denomination to the fish described by Hasselquist, not 

 having been aware that the Swedish traveller mentions the horn of the forehead 

 in his description onlj in the passage which is headed " Branchiee." 



