n the _comminuted recent shells_ of
the boulder-clay as in the belemnites of the Oolite and Lias, or the
ganoid ichthyolites of the Old Red Sandstone.

I had marked, when at Wick, on several occasions, a thick boulder-clay
deposit occupying the southern side of the harbor, and forming an
elevated platform, on which the higher parts of Pulteneytown are built;
but I had noted little else regarding it than that it bears the average
dark-gray color of the flagstones of the district, and that some of the
granitic boulders which protrude from its top and sides are of vast
size. On my last visit, however, rather more than two years ago, when
sauntering along its base, after a very wet morning, awaiting the Orkney
steamer, I was surprised to find, where a small slip had taken place
during the rain, that it was mottled over with minute fragments of
shells. These I examined, and found, so far as, in their extremely
broken condition, I dared determine the point, that they belonged in
such large proportion to one species,--the _Cyprina islandica_ of Dr.
Fleming,--that I could detect among them only a single fragment of any
other shell,--the pillar, apparently, of a large specimen of _Purpura
lapillus_. Both shells belong to that class of old existences,--long
descended, without the pride of ancient descent,--which link on the
extinct to the recent scenes of being. _Cyprina islandica_ and _Purpura
lapillus_ not only exist as living molluscs in the British seas, but
they occur also as crag-shells, side by side with the dead races that
have no place in the present fauna. At this time, however, I could but
think of them simply in their character as recent molluscs; and as it
seemed quite startling enough to find them in a deposit which I had once
deemed representative of a period of death, and still continued to
regard as obstinately unfossiliferous, I next set myself to determine
whether it really _was_ the boulder-clay in which they occurred. Almost
the first pebble which I disengaged from the mass, however, settled the
point, by furnishing the evidence on which for several years past I have
been accustomed to settle it;--it bore in the line of its longer axis,
on a polished surface, the freshly-marked grooves and scratchings of the
iceberg era. Still, however, I had my doubts, not regarding the deposit,
but the shells. Might they not belong merely to the talus of this bank
of boulder-clay?--a re-formation, in all probability, not _mo