of the
shell remains in most instances as distinct as if it had undergone no
mineral change. I have seen nowhere in Scotland, among the secondary
formations, so unequivocal an oyster-bed; nor do such beds seem to be at
all common in formations older than the Tertiary in England, though the
oyster itself is sufficiently so. We find Mantell stating, in his
recent work ("Medals of Creation"), after first describing an immense
oyster bed of the London Basin, that underlies the city (for what is now
London was once an oyster-bed), that in the chalk below, though it
contains several species of Ostrea, the shells are diffused
promiscuously throughout the general mass. Leaving, however, these
oysters of the Oolite, which never net inclosed nor drag disturbed,
though they must have formed the food of many an extinct order of
fish,--mayhap reptile,--we pass on in a south-western direction,
descending in the geological scale as we go, until we reach the southern
side of the Bay of Laig. And there, far below tide-mark, we find a
dark-colored argillaceous shale of the Lias, greatly obscured by
boulders of trap,--the only deposit of the Liasic formation in the
island.

A line of trap-hills that rises along the shore seems as if it had
strewed half its materials over the beach. The rugged blocks lie thick
as stones in a causeway, down to the line of low ebb,--memorials of a
time when the surf dashed against the shattered bases of the trap-hills,
now elevated considerably beyond its reach; and we can catch but partial
glimpses of the shale below. Wherever access to it can be had, we find
it richly fossiliferous; but its organisms, with the exception of its
Belemnites, are very imperfectly preserved. I dug up from under the
trap-blocks some of the common Liasic Ammonites of the north-eastern
coast of Scotland, a few of the septa of a large Nautilus, broken pieces
of wood, and half-effaced casts of what seems a branched coral; but only
minute portions of the shells have been converted into stone; here and
there a few chambers in the whorls of an Ammonite or Nautilus, though
the outline of the entire organism lies impressed in the shale; and the
ligneous and polyparious fossils we find in a still greater state of
decay. The Belemnite alone, as is common with this robust fossil,--so
often the sole survivor of its many contemporaries,--has preserved its
structure entire. I disinterred from the shale good specimens of the
Belemnite _sulcatu