1 35 2 Catalogue of Malayan Fishes. [Dec. 



D9, C81, A 9, P 11, Br. VI. 



Habit. — Sea of Pinang, Malayan Peninsula. 



" Indian and American Seas/' (Bloch.) 



Total length : 7f inch. 



The form is nearly quadrangular, as the breadth of the abdomen but 

 slightly exceeds that of the back and the height of the sides. The 

 back is elongated lanceolate ; from the nasal protuberance the profile 

 gently ascends towards the middle of the back, when it slowly descends 

 towards the tail, the whole forming a very low arch. From the occiput to 

 near the dorsal the middle of the back is raised and forms a low triangu- 

 lar keel, on each side of which appears a shallow broad sulcus, outside 

 bordered by the raised angular margin of the side. The triangular 

 forehead slopes gently from the occiput and appears a little excavated 

 owing to the broad protuberant supraorbital margins. The breadth 

 between the anterior angles of the orbit is § of the length of the head ; 

 between the posterior angles it equals the head ; the greatest breadth, 

 in the middle of the back, exceeds the length of the head by ^, £ or £, 

 according to the individually more or less projecting nasal protuberance ; 

 the breadth at the termination of the armour is a little less than half 

 the breadth between the posterior orbital angles. The nasal protuber- 

 ance is blunt, rounded. In individuals 6f inch in length it scarcely 

 projects beyond the mouth, immediately above which the profile rises 

 vertically, and this portion measures ^ of the distance between the ante- 

 rior angle of the orbit and the protuberance, which in them is i of the 

 total length. In the largest individual, 7f inch in length, the protu- 

 berance perceptibly projects beyond the mouth, from which the profile 

 projects obliquely and exceeds £ of the stated distance, which is J of the 

 total length. The sides are but little excavated ; their greatest vertical 

 diameter corresponds to, but slightly exceeds, the greatest breadth of 

 the back ; it varies from 4 J to A\ times in the total length. The length 

 of the head, from the nasal protuberance to the gill-opening, is in young- 

 er individuals, with the protuberance but little developed, \ of the total, 

 in older ones it is contained 4| times in the total. The eye is close to the 

 profile ; the posterior angle of the orbit is situated above the gill-opening. 

 The greatest diameter is a little oblique, ascending backwards ; it is con- 

 tained 1\ times in the distance from the mouth to the gill-opening, and 

 this proportion appears to be constant. But as the development of the 



