272 Proceedings of the Royal Physical Society. 
centre is rather in front of the eyes. Each diagonal of this 
area measures 6 inches. 
The outer layer of the shield is unfortunately not present 
over much of the surface, though its ornamentation is here 
and there visible. This ornamentation consists of an exces- 
sively minute tuberculation, which is, however, coarser and 
more marked round the edges of the shield, and of the orbits 
(Pl. VIL, Fig. 2), as well as along the inner margin of the cornu. 
The pseudo-tessellation of the middle layer is well seen, the 
tesseree (Fig. 4) being mostly 4 to 4 inch in diameter, which 
is very small in proportion to the size of the shield. The 
specimen exhibits no trace of the radiating vascular canals 
usually seen in connection with the inner layer of the shield 
in Cephalaspis. The body remains are too obscure for 
description, but clear evidence is afforded of a tubercular 
ornament of the scales, similar to that of the cranial shield. 
Cephalaspis magnifica, the largest representative of the 
genus at present known, ‘may be readily distinguished from 
all previously described species. It is the only species 
besides C. Canvpbelltownensis, Whiteaves, which has a pointed 
snout, but this pointing is not nearly so prominently developed 
as in that Canadian form. The orbits are also proportionally 
smaller and farther apart than in C. Campbelltownensis, and 
the cornua, instead of being long and curved, are compara- 
tively short and broad-based. 
The above-described specimen is not merely a unique 
example of a new species of fossil fish, but, as mentioned at 
the beginning of this paper, it constitutes the first recorded 
occurrence of a fish of the family Cephalaspidee in the rocks 
of the Orcadian area of Old Red Sandstone. But the dis- 
covery of a species of Cephalaspis in the Caithness Flags has 
no important bearing on the question of the age of the 
Lower Old Red Sandstone of this area, relative to that of the 
“ Caledonian” area of Central Scotland, or of the “ Welsh” 
area of the West of England and adjoining parts of Wales. 
For the occurrence of another species of Cephalaspis (C. 
‘laticeps, Traq.) in the Upper Devonian rocks of Canada,} 
1R. H. Traquair in Geol. Mag. (3), 1890, vol. vii., p. 16. 
