276 PISCES. 



pelvis, which is completely hidden under the skin and is without 

 that spinous projection observed in the other Balistes.(l) 



Triacanthus, Cuv. 



Is distinguished from all other Balistes by a kind of ventrals, each 

 of which is supported by a single large spinous ray, adhering to a 

 non-salient pelvis. The first dorsal has three or four small spines 

 behind a very large one. The skin is crowded with small scales, 

 and the tail is longer than in the other subgenera. 



But a single species is known; it inhabits the Indian Ocean.(2) 



OsTRACiON, Lin. 



The head and body of these fishes, instead of scales, are covered 

 with regular bony plates soldered in such a manner as to form a sort 

 of inflexible shield, which invests them, so that the only movable 

 parts are the tail, fins, mouth, and a sort of small lip with which 

 the edge of their gills is furnished, all passing through holes in this 

 coat of mail. The greater number of their vertebrae are also sol- 

 dered together, and each of their jaws is armed with ten or twelve 

 conical teeth. The external branchial aperture is a mere slit fur- 

 nished with a cutaneous lobe, but internally we find an operculum 

 and six rays. Both the pelvis and ventrals are wanting, and there 

 are but a single dorsal and ventral, both small. 



They have but little flesh; their liver, however, is large and pro- 

 duces much oil. Their stomach is membranous and large; some of 

 them are considered poisonous. 



They may be divided according to the form of their body and the 

 spines with which it is armed; we are not certain, however, that 

 there is not, in this respect, some sexual difference.(3) 



(1) Bui. monoccros, L., Catesb., 19; — the monoceros of Bl., \Thich is different, 

 147; — Bal. kevis, BI., 414; — Acaramucu, Marcgr., 163, also differing- from the 

 three preceding ones;— i?a/. Kleinii, Misc. Ill, pi. iii, f. '2\—M. cryptaeanthus, 

 Cuv., Uen., II, part of pi. xlii, f. 284. 



(2) Bal. biacukatus, lU., 148, 2. 



Numerous species of all these subgenera will be described in our Hist, des 

 Poissons. 



(3) 1st. A triangular body without spines. Ost. triqueter, Bl., 130; — Ost. conca- 

 tenatus, Bl., 131. 



2d. A triangular body armed with spines behind the abdomen. Ost. bicaudalis, 

 Bl., 132; — Ost. trigonus, Bl., 135. 



3d. A triangular body armed with spines before and behind the abdomen. Ost. 

 quadricornis,B]., 134. 



4th. Triangular, the ridges armed with spines. Ost. stelUfer, Schn., 97; the 

 same as tiie Ost. hiatspis, Blumenb., Abb., 58. 



