OSTRACION BICUSPES. 



of cuirass semicircular, the convexity forwards. Under surface nearly flat, 

 and somewhat diamond-shaped ; the greatest width a little way behind the 

 commencement of the second third of the body ; the hinder extremity of the 

 under surface broad and triangular, its termination directly under the point 

 which forms the upper elongation. The lateral or abdominal angles spread- 

 ing particularly towards the middle of the cuirass ; towards the head they are 

 rather obtuse, elsewhere thin and sharp, and each, when perfect, is armed with 

 two or four short and slender spines, the longest and strongest of each side 

 situated at the most diverging point, as represented in figure a. The plates 

 of the cuirass are irregularly six or seven sided, and the surface of each is 

 divided into six or seven somewhat triangular compartments, by the same 

 number of narrow rugose ridges radiating from a common centre, and each 

 compartment, like the ridges, is more or less rugose, from the existence of a 

 number of small semi-circular granules. In consequence of a certain degree 

 of regularity in the arrangement of some of these ridges, an appearance is 

 produced as if the sides were crossed longitudinally by several rows of long, 

 narrow, and oval compartments, arranged like links of a chain. The plates 

 of the under surface six-sided ; those towards the head closely coated with 

 granules ; those on the belly with four or six divergent ridges, and only a very 

 few granules. Tail subcylindrical ; dorsal, pectoral, and anal fins square 

 behind, and the first ray of each the longest ; caudal fin posteriorly slightly 

 rounded, or square. 



DIMENSIONS. 



In. Lin. 



Length from the point of the nose to 



the hinder edge of the caudal fin ... 10 



Distance between the hinder angle of the 



eye, and the base of the dorsal fin . . . 4 3 



In. Lin. 



Distance between the hinder angle of the 



eye, and the base of the anal fin ... 4 9 



Distance between the nose and the bran- 

 chial opening 1 10| 



In very young specimens (fig. b), the superciliary ridges are arched, sharp, 

 and armed with two delicate compressed spines. The arch of the back is 

 greater than in adults, and the abdominal angles are more expanded 

 horizontally. 



Inhabits the seas of Southern Africa, and found most frequently in the bays of the South- 

 eastern coast. 



