138 
THE GEOLOGIST. 
nally by small hexagonal ganoid scales. Near the centre of this shield 
two rather closely placed holes formed the orbits for the eyes. In one 
of the heads in my possession the eye-balls are finely preserved 
completely petrified ; between the eyes were two ridges having an 
intermediate hollow or sinus extending from the eyes backwards. 
One of my specimens shows that these ridges united towards the 
posterior edge of the shield, forming evidently a strong defence. 
Kone of the many heads I have examined show the slightest evidence 
that this creature was possessed of teeth, or a mouth of the ordinary 
form ; this organ, I believe, being similar to the sturgeon, w^hich royal 
fish, I have little doubt, had this comparatively small creature as its 
representative in these old world waters. Some of the cusps or 
shai^ened points of the shield are very much elongated and toothed 
on the interior of the margin. The body as compared with the head 
was but small, very slender, and protected by bony rings, extending 
in a slanting direction from the back downwards, these again being 
covered by exceedingly minute rhomboidal scales ; in this respect 
resembling the larger number of the fishes found in the lower beds of 
the Forfarshire Old Red, as Climatius, Acanthodes, Viplacantlms, &c. 
In only one specimen have I ever observed these on all scales ; but a 
portion of one in my possession shoAvs a very perfectly preserved 
cast of them : its heterocercal tail was much produced and furnished 
with a very large and powerful fin. None of the specimens I have 
as yet examined show the slightest vestige of either anal or ventral 
fins. The existence of a dorsal is by no means established ; had it 
existed it must have occupied a position very far back. This creature 
w^as, however, further remarkable for having two very large membra- 
nous pectorals, attached immediately under the cephalic buckler, 
seemingly of a leathery consistence, and covered by small sub -circular 
or hexagonal scales. The pectorals were first discovered by me, in 
the specimen from which the figure is copied. 
The remains of Cephalaspis, generally associated with plates or 
other portions of the Pterijgotus Anglicus, have been found in alnost 
aU the places where the gi^ey flagstones, generally known in commerce 
as the Arbroath pavement, and which crop out in so many localities 
in Forfarshire, have been wrought. It has also been found in a bright 
red micaceous sandstone, overlying and considerably above these 
flagstones, while in no case has the Pterygotus Angllcus been, up to 
this time, found in the sandstones overlying the shales and flagstones 
of the Arbroath pavement. Although the above-mentioned flagstones 
are quarried in so very many places in Forfarshire, anything ap- 
proaching to a complete specimen of this fish very rarely turns up 
indeed. I only know of some eight or ten specimens showing the 
body, having been as yet disinten^ed from the rocks in wliich they 
have so long been intombed. Perhaps the finest of these was several 
years ago got by the late Mr. Lindsay Carnegie from his quarries at 
Leysmill, and by him presented to the Arbroath Museum. The well- 
known specimen presented by Sir Charles Lyell to the British 
Museum was found in a quarry near the \allage of Glanmis. There 
