DR. RICHARDSON'S DESCRIPTION OF AUSTRALIAN FISH. 159 



by a waving line which runs round the vertical fins so as to leave them all in soft mem- 

 brane. The pectorals also stand in smooth membranous spaces. The tail is protected 

 by the usual number of coarsely granular plates which form two rings. 



The plates which compose the cuirass vary in size with their position, being smallest 

 round the mouth and towards the dorsal and ventral ridges. They are mostly irregular 

 hexagons, but many of them have a side more, and some one or two less. A wart-like 

 umbo occupies the centre of each plate, as many ridges proceed from it as the plate 

 has angles, and are continued to the centres of the contiguous plates. The plates are 

 simply in contact with each other, their margins not being thickened, and when the 

 epidermis is entire their boundaries are invisible ; but the radiating ridges which connect 

 their centres are very conspicuous, and divide the whole cuirass into triangular areas of 

 various sizes, each area being common to three adjoining plates. The umbones and 

 ridges are formed of rounded, crowded, or confluent grains, and are most elevated in 

 the younger specimen. In the older fish they are attenuated and less prominent, and 

 the areas of the triangles which have expanded with the increased size of the animal, 

 are studded with small grains, which are scarcely discernible in the young one. 

 There is likewise in the old fish a series of ridges more prominent than the rest, 

 so disposed as to form nearly a straight line from beneath the pectoral to near the 

 hinder part of the anal, with five or six of the umbones rising rather acutely into inci- 

 pient spines ; and there is also a less evident but more arched line of the same kind 

 from the upper margin of the orbit to beneath the middle of the dorsal. These two 

 lines evidently correspond to those which define the back and belly in the typical 

 Aracanee, and on which the strong spines of the cuirass stand. The principal lateral 

 spine of the Aracarue is represented in Ostracion lenticularis, when old by an acute umbo 

 on the centre of each side, in the middle of the greatest vertical height, being rather 

 above the level of the pectoral. 



Radii— F. 12; D. 10; A. 10; C. 11. 



The fins are similar in form to those of the Aracante, but differ somewhat in the 

 number of rays from the Van Diemen's Land species, which have eleven for the normal, 

 though not invariable number of rays in all their fins. We have reckoned the first 

 very short pectoral ray in the present species and in the Aracana. 



The only remains of colour in either of Dr. Smith's specimens is an olive, ground tint 

 near the back, some scattered, round blotches on the upper part of the body, and a few 

 stripes of purphsh-brown on the dorsal and caudal fins. 



Dimensions. 



In. Lin. 

 Length from upper lip to tip of caudal fin of the older specimen . 6 7 



Length from upper lip to base of caudal fin 5 2 



Length from upper hp to beginning of dorsal or anal .... 4 2^ 



Length from upper lip to pectoral fin 18^ 



y2 



