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AT ST. ERTH, XE.iR LAND S END, CORNWALL.
67
put these specimens into my hands, as "well as some more that he
had subsequently procured, and sent me his note-book with the
sections, but, to satisfy my inquiry as to the elevation of the bed,
visited the spot again, and ran a set of levels from mean tide-mark
on the Hayle shore to the pit, by which he ascertained that the
elevation of the part from which he obtained his specimens is 98
feet above ordnance datum, the surface of the ground being about
15 feet higher.
Fig. 2. — Section across the Valley of the Hayle at St. Erth.
W.N.W.
Trecobben Hill.
590 feet.
E.S.E.
The Hajle
Estuary. St. Erth
Sea-leTel.
a, a. Ancient rocks. h. Eecent and Prehistoric silt.
Line shov^ing the probable surface of the sea in the strait in which tlie
St. Erth shells lived.
The pits are on the eastern slope of a tract of low ground that
extends from Penzance and Marazion on the south coast, to St. Ives
Bay on the north coast of the county, cutting off the high ground of
the Land's End district from the rest of Cornwall. The bottom of
this low tract is occupied by beds of peat and of estuarine or
marine silt, altogether unconnected with the bed in question, and
which, from the specimens of Mollusca sent to me by ITr. Cornish
from some excavations in them, appear to be of that recent date
which marks the last depression of Britain * and belongs to the
iSTeoKthic period.
As this tract cuts through the highland formed of ancient rocks,
it must at the time of the deposit of the St. Erth beds have been a
strait, separating the Land's End region from the mainland of
Britain ; but no other indication of this deposit has hitherto been
detected.
.The author here added a provisional list of Mollusca obtained by
him to the number of about 50. As this list was confessedly im-
perfect, he expressed his intention of preparing and publishing
hereafter a full description of the fauna, with figures of the new
species; it was withdrawn by him with the permission of the
Council,.
Of the species obtained by me from the bed, three, viz. Cyprcea
avellana, Nassa granulata, and Melampus .pyramidalis, are Eed-

• The succession of events traced in my memoir on the Newer Pliocene
  

period in England, Q, J. Gr. S, vol. xxxviii. p. 732, terminates j ust prior to this
last depression, which is only briefly adverted to, and then only in respect of
the amount of depression that has taken place.