96 " THETIS " SCIENTIFIC RESULTS. 



broadly fan-shaped with the angles rounded, the lower rays longer 

 than the upper. 



Carapace much compressed, forming a ridge above and below 

 and two scarcely perceptible ridges, one from behind the eye and 

 the other beneath the pectoral. The carapace terminates in 

 advance of the dorsal fin and passes obliquely back wards on each side 

 by a sinuous line towards the posterior part of the anal ; skirting 

 the base of that fin, it passes forward and again unites with its 

 fellow in advance of the anal. The carapace is composed of hex- 

 agonal scutes fused together, most apparent on the sides and 

 around and beneath the mouth. From the upper and lower 

 angles of the mouth are two naked lines which unite and form an 

 unprotected area in front of the gill opening and pectoral fin, thus 

 permitting some movement ; the lips also are free and fleshy. 

 The whole of the space from before the dorsal and anal to the caudal 

 is naked, with the exception of four bony plates; a large one imme- 

 diately behind the dorsal fin, widely separated from a similar but 

 smaller plate behind the anal. A. third on the upjDer part of the 

 caudal pedicel in front of the rays which extends to but is not 

 fused with another jolate on the lower part; a few isolated patches 

 of armature also occur on the pedicel. All the scutes closely 

 granular, the grains larger than the spaces between them. 



Golom\ — Uniform greenish-brown. 



Young. — Profile of snout straight, interorbital space concave, 

 caused by enlarged supraocular borders, dorsal profile regularly 

 rounded without hump. The dorsal and anal keels are much more 

 compressed than in the adult and all the features of the carapace 

 more pronounced : the lateral ridges are continued, the upper 

 from above the eye to the dorsal fin, and the lower from the 

 angle of the mouth beneath the pectoral to the anal. These 

 ridges are armed with prominent flattened spines arranged as 

 below. One above the posterior angle of the orbit, one a little 

 further behind, another beneath the highest point of the dorsal 

 ridge and a very small one nearer the dorsal fin ; there are three 

 or four spines along the lower ridge, of which the first is below 

 the pectoral and the last in advance of the anal. The largest 

 spine of the body occurs on the side midway between the two 

 ridges in the centre of the carapace. The naked groove from the 

 mouth to the gill opening is apparent only as a non-fusion of the 

 scutes and the space around the pectoral, and the mouth is very 

 restricted. The hexagonal plates are most apparent and have 

 large granules forming radiating ridges, the grains widely spaced. 



C'olou)'. — Lilac with metallic yellow blotches arranged without 

 reference to th(^ scutes, which ai'e boldly outlined in black. Naked 

 skin slaty-grey. Fins brown, the caudal durkcr witli a lighter 

 margin. 



