THE FISHES OF MALABAR. 
253 
Order.— P LECTOGNATHI. 
Sub-Order.— OSTEACIONIDvE. 
Fam. OSTRACIONOIDEI, BleeJcer. 
Genus OSTEACION, Linn. 
L^etopiirys, et tetrosomus, Swainson. 
Acanthostracion, Meeker. 
Branchiostegals, six. Body shortened and angular, invested by a solid covering composed of fibro- 
osseous angular plates placed in juxtaposition, leaving holes for the mouth, eyes, gill-openings, dorsal, 
anal, and caudal fins. Each jaw with from ten to twelve conical teeth ; the maxillae and intermaxillae are 
intimately soldered together. Dorsal fin single, short, or absent. Ventrals none. 
The genus is divisible into four subgenera, 1 . Ostracion, in which the species are destitute of spines : 
2. Lcctophrys, with the sides of the ventral keel posteriorly armed with spines : 3. Tetrosomus, preorbital 
spine directed upwards, and ventral keel spinate, or armed posteriorly by a strong spine; in some the 
posterior superior extremity of the carapace transformed into a strong spine: 4. Acanthostracion, preorbital 
spines directed forwards. Ventral keel posteriorly armed with a strong spine : in some the dorsal keel is 
also armed with a strong spine, in others the spines (except the anal) are absent. 
Ostracion nasus. 
Ostracion nasus, Bloch , t. 138; Bleeker , Atl. Icli. v. p. 36, t. 202, f. 5. 
Ostracium tesserula, Cantor , Catal. p. 367, pi. viii. f. 2, 3, (immature.) 
B. vi. D. 9. P. 10. A. 9. C. 8 . L. 1. 12. L. tr. 5. 
Length of head f, of pectoral of caudal f of the total length. Height of head ^, of body 
above jr, of dorsal of anal of the total length. 
Eyes—Hot far from profile : diameter -3 of the length of the head, 1 diameter from end of 
snout. 
Body tetragonal, the back elongated, forming rather a long oval, and slightly convex, owing 
to its having a raised longitudinal crest, which is most prominent near to the base of the dorsal fin. 
The transverse diameter across the back is rather more than the height of the body, the abdominal 
surface is slightly broader. The vertical diameter of the sides is concave, much more so in the 
very young, as eight-tenths of an inch in length, than in another twice that length; also there is a 
concave groove along either side of the mesial crest of the body between it and the superior 
lateral ridge. 
Teeth—In the Cochin specimens only eight in each jaw; sharp, rather distant, red and 
gleaming: some are probably absent, as there should be twelve in the upper and ten in the 
lower jaw. 
Lips fleshy. 
Fins—The dorsal is situated in the posterior sixth of the back, the anal rather behind it. 
Caudal rather broad and rounded at its extremity. Pectoral broad and fan-shaped. All the rays 
are unbranched. 
