1350 Catalogue of Malayan Fishes. [Dec. 



iris bright gamboge, orbital margin orange ; in the middle of the upper 

 pupillary margin a small notch. 



D 9, C 8|, A 9, Br. VI. 



Habit. — Sea of Pinang, 



Total length : 2 inch. 



The general form is tetragonal. The back is elongated oval, arched 

 from the occiput to the tail ; in the centre appears a short longitudinal 

 crest, on each side of which is a deep furrow, laterally bounded by the 

 sharp angular margin. By these three crests the vertical section in 

 this particular region becomes pentagonal. The profile of the forehead 

 is nearly straight and steep. The distance between the anterior angles 

 of the orbits is \ of the total length ; the greatest breadth in the middle 

 of the back is contained 2f times in ; above the naked tail it is ^ T of the 

 total length. The abdominal surface is both longitudinally and trans- 

 versely arched, with a furrow along the angular margin ; it is broader 

 than the back, its greatest breadth, beneath the pectorals, varies from 

 If in to J of the total length. The sides are excavated with the lower 

 margin projecting farther outwards than the upper ; their greatest diame- 

 ter is nearly in the middle and is contained 2 J times in the total length ; 

 but the vertical diameter of the central crest of the back is a little longer, 

 ©wing to the central convexity of the abdomen. The armour is composed 

 of hexagonal pieces with very finely toothed or ciliated margins. From 

 the centre of each hexagon radiate towards the margins six raised lines 

 of which the central, horizontal ones, join their neighbours, so as to 

 form on the sides of the armour seven parallel, horizontally arched, lines, 

 which form the bases of triangles produced by the other obliquely 

 radiating lines. On the back and sides the triangles are very conspicuous, 

 while the hexagonal outline of the component pieces can scarcely be 

 traced. On the abdominal surface the reverse is the case. From the 

 central tubercle radiate numerous fine lines j but the triangles are very 

 indistinct. The length of the head is contained a little less than 3^ 

 times in the total. The eye is situated close to the profile, nearly in 

 the middle between the gill-opening and the muzzle ; the horizontal 

 diameter is ^ of the length of the head. The supraorbital arch forms 

 a tubercular protuberance. The mouth, teeth, and tongue and nostrils 

 resemble those of O. cornutum, but there appears to be no nasal papilla. 

 The dorsal is placed close to the termination of the armour; the 



