g, and
possess others. These differences may and do exist in contemporary
deposits; and I had a striking example, on this occasion, of their
dependence on a simple law of instinct, which is as active in producing
the same kind of phenomena now as it seems to have been in the earlier
days of the Old Red Sandstone. The Cromarty and Moray Friths, mottled
with fishing boats (for the bustle of the herring fishers had just
begun), stretched out before me. A few hundred yards from the shore
there was a yawl lying at anchor, with an old fisherman and a few boys
angling from the stern for sillocks (the young of the coal-fish) and for
small rock-cod. A few miles higher up, where the Cromarty Frith expands
into a wide landlocked basin, with shallow sandy shores, there was a
second yawl engaged in fishing for flounders and small skate,--for such
are the kinds of fish that frequent the flat shallows of the basin. A
turbot-net lay drying in the sun: it served to remind me that some six
or eight miles away, in an opposite direction, there is a deep-sea bank,
on which turbot, halibut, and large skate are found. Numerous boats were
stretching down the Moray Frith, bound for the banks of a more distant
locality, frequented at this early stage of the herring fishing by
shoals of herrings, with their attendant dog-fish and cod; and I knew
that in yet another deep-sea range there lie haddock and whiting banks.
Almost every variety of existing fish in the two friths has its own
peculiar habitat; and were they to be destroyed by some sudden
catastrophe, and preserved by some geologic process, on the banks and
shoals which they frequent, there would occur exactly the same phenomena
of grouping in the fossiliferous contemporaneous deposits which they
would thus constitute, as we find exhibited by the deposits of the Lower
Old Red Sandstone.

The remains of Holoptychius occur, I have said, in the neighborhood of
Thurso. I must now add, that very singular remains they are,--full of
interest to the naturalist, and, in great part at least, new to Geology.
My readers, votaries of the stony science, must be acquainted with the
masterly paper of Mr. Sedgwick and Sir R. Murchison "On the Old Red
Sandstone of Caithness and the North of Scotland generally," which forms
part of the second volume (second series) of the "Transactions of the
Geological Society," and with the description which it furnishes, among
many others, of the rocks in the neighborhood