140 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 24,
elsewhere, although in their
distribution there is something
peculiar. The definite separation
into zones is rather difficult.
The upper limestones, in
which alone Am. angulatus is
found, contain a varied fauna,
with which there is nothing to
compare in the beds below.
It is certain, however, that only
the lower part of this zone is
here exposed. Am. Johnstoni,
however, ranges through these
and the limestones lower down,
and is here the most characteristic
Ammonite. The true Am.
planorbis has as yet been found
only in one bed ; but this is not
separated from the others by
any other features. The change
to the oyster-bands is very
marked in pit No. 3,. accompanied
as it is by a cessation
of microscopic fossils ; and the
same may be said of the change
into the white limestone beds
below.
On comparing the " angulatus" fauna with that of Marton, it will now be seen how nearly allied they are — so much so that it is probable that a complete knowledge of both would prove them to be almost perfectly identical. As at present known, however, they present some decided differences. Of the 44 species recorded as certain from Marton, 23 are also found at Cliff; and it appears possible that an actual comparison of specimens would increase this proportion. Fifty-two species are here recorded as certain from the same horizon, excluding vertebrates and microscopic fossils; of these 15 belong to genera unrepresented at Marton. The difference consists chiefly in the
