206 Mr. R. Walker on Clays, containing Fossils, 
marsh- and perhaps other plants had grown and decayed (how 
long, it would be impossible to conjecture) before the land again 
began to sink under the sea; during which time the deposit 
would be exposed to the tear and wear of the waves, when doubt- 
less many of the organisms, together with a great portion of the 
bed itself, would be washed away. It would be difficult to ascer- 
tain, from the manner in which the third and second beds seem 
to have been deposited, to what extent the land subsided at the 
time, and whether the subsidence was gradual or rapid. The 
continuation of the latter of these beds has been noticed at 
other places in the neighbourhood, at greater elevations. For 
instance, in a cutting to divert a small stream on the farm of 
St. Nicholas, about half a mile south of the clay, this littoral 
deposit was passed through: here it is from 12 to 15 inches in 
thickness; and the composition and contained fossils are iden- 
tical with the second bed of the section. At this part the de- 
posit is laid upon a gentle declivity arching round to the 
Kinness valley, and from 27 to 30 feet above the sea, thus 
occupying an intermediate position between Dr. Chambers’s 
64-feet beach at this place and the sea-level ; he states, however, 
that here ‘‘ the sea has made several shifts of level without in- 
denting the land”’*. This stratum was likewise exposed, on the 
north side of the Kinness valley, about three vears since, while 
altering a wall at the gas-works, at an elevation of 35 feet above 
the sea, the ground sloping towards the south. This bed was 
again laid open by the present drainage-excavations ; but this. 
time it was on the west side of St. Andrews, at the height of 
21 ‘feet above the sea, and contained all the littoral shells enu- 
merated in our second bed. 
Besides the preceding, there is additional evidence, though of 
a different kind, of the sea having stood at a higher level than 
at present, in recent times, geologically speaking. This is fur- 
nished by an isolated patch of sandstone that crops out at the 
south end of the “west sands ” being quite full of the holes of 
Pholas crispata. This rock is within a foot or two of high-water 
mark, and about 14 feet above the habitat of the Pholas at the 
present day, which generally lives between 2 to 3 feet above low- 
water mark and a few fathoms beyond. They do not appear 
from choice to make their habitations in sandstone, but rather 
prefer shale or limestone, if these rocks can be had at suitable 
depths. From the numerous borings in the sandstone in ques- 
tion, it would seem that it had continued for a long time at a 
depth in the water favourable to the organization of these mol- 
lusks ; and as the land was gradually elevated, they appear, from 
their holes still visible here and there in the intervening rocks, 
* Ancient Sea Margins. 
