rk on the Old Red Sandstone will
perhaps remember that I described the organisms of that ancient system
as occurring in the neighborhood of Cromarty mainly on one platform,
raised rather more than a hundred feet over the great Conglomerate; and
that on this platform, as if suddenly overtaken by some wide-spread
catastrophe, the ichthyolites lie by thousands and tens of thousands,
in every attitude of distortion and terror. We see the spiked wings of
the Pterichthys elevated to the full, as they had been erected in the
fatal moment of anger and alarm, and the bodies of the Cheirolepis and
Cheiracanthus bent head to tail, in the stiff posture into which they
had curled when the last pang was over. In various places in the
neighborhood the ichthyolites are found _in situ_ in their coffin-like
nodules, where it is impossible to trace the relation of the beds in
which they occur to the rocks above and below; and I had suspected for
years that in at least some of the localities, they could not have
belonged to the lower platform of death, but to some posterior
catastrophe that had strewed with carcasses some upper platform. I had
thought over the matter many a time and oft when I should have been
asleep,--for it is marvellous how questions of the kind grow upon a man;
and now, selecting as a hopeful scene of inquiry the splendid section
under the Northern Sutor, I set myself doggedly to determine whether the
Old Red Sandstone in this part of the country has not at least its two
storeys of organic remains, each of which had been equally a scene of
sudden mortality. I was entirely successful. The lower ichthyolite bed
occurs exactly one hundred and fourteen feet over the great
Conglomerate; and three hundred and eighteen feet higher up I found a
second ichthyolite bed, as rich in fossils as the first, with its thorny
Acanthodians twisted half round, as if still in the agony of
dissolution, and its Pterichthyes still extending their spear-like arms
in the attitude of defence. The discovery enabled me to assign to their
true places the various ichthyolite beds of the district. Those in the
immediate neighborhood of the town, and a bed which abuts on the Lias at
Eathie, belong to the upper platform; while those which appear in Eathie
Burn, and along the shores at Navity, belong to the lower. The chief
interest of the discovery, however, arises from the light which it
throws on the condition of the ancient ocean of the Lower Old Red,