So we may have in such an area marine beds partaking of 
the characters of the oldest drifts, but, when looked into care- 
fully, obviously of later date, and only made up of the debris 
of the older drift. 
It is quite possible that the beds described by Mr. Shone, 
from lower ground near Chester, may be older than those in 
the Yale of Clwyd, and distributed along the straits before 
the land rose high enough to form the estuary of the Clwyd, or 
it may be that northern currents kept a more arctic fauna here 
and there, or perhaps they were in part derived from older 
Glacial beds. The reason of the more arctic character of the 
Chester beds is not quite clear. 
Now, if we follow these beds to the east we shall find 
similar sands and gravels, but perhaps more largely derived 
in some places from the Trias sandstone, half-across England. 
On the north the bounding shore is not so clear as round the 
hills of Wales. The beds of Macclesfield, we have seen, cor- 
respond with those of Moel Tryfaen, and the shells are much 
the same. 
Still more to the east and a little further north we find the 
marine sands of Kelsea Hill containing a not very arctic type 
of shells, while in the old boulder clay of Dimlington Hill on 
the coast north of Holderness, in company with Mr. Leonard 
Lyell, I found a small lenticular mass of sand full of shells 
such as occur in what used to be called the Bridlington Craof. 
There were among them Nucula Cobboldim and Astarto 
compressa, with the two valves united, and other decidedly 
arctic forms. These shells are now in Mr LyelFs collection 
who gives the following list : — 
Saxicava rugosa. 
Astarte borealis. 
A. compressa (young, both valves united). 
Nucula Cobboldias. 
Turritella (from clay). 
Cyprina Islandica. 
Tellina balthica. 
Mya. 
Fusus striatus (from clay). 
Here I take it we have, far away from the high mountains, 
evidence in the one deposit of the time when the sea was 
chilled and arctic life prevailed, in the other deposit record of 
the time when changes of level had let in warmer currents, 
and the temperate forms of life. 
These movements extended north through Scotland, where 
traces of shell-bearing sands are recorded up to 500 feet, and 
