384 
area was linked with the Sherborne district, not only during 
the time of the Murchisone- and Concavum-zones, but also 
during the Humphriesianum-zone, and that such links have been 
removed, possibly by the agency which deposited the Alluvium 
to the westward of Glastonbury. 
The Lias which extends along the Glamorganshire coast— 
up the Bristol Channel to the Tortworth barrier — around 
Dundry—and down the North Somerset coast—was probably 
all covered by the Inferior-Oolite sea. So also were the districts 
drained by the Parret and the Axe. If, then, we restore the 
Inferior-Oolite over all the country mentioned, we soon see the 
connection between the Dorset-Somerset area and Dundry. 
During the deposition of the Humphriesianum-zone we may 
imagine a narrow trough of the sea stretching from Bayeux in 
Normandy, to Burton Bradstock, to Sherborne, and round the 
western end of the Mendips to Dundry, as the area where sedi- 
ment was being deposited. 
With the advent of the Parkinsoni-zone a great change 
must have occurred not only in the Cotteswold, but also 
in the Dorset-Somerset area. A very great subsidence of land 
is proved to have taken place by the fact that deposition was 
actively carried on, not only over all the previous Inferior- 
Oolite areas, but over what had hitherto been dry land. 
The Tortworth barrier and the southern isthmus become sub- 
merged, and the sea covers a greater portion of the Mendip Hills 
than it had done previously—this being shewn by the fact of 
the Parkinsoni-zone resting on the Carboniferous. At this time 
it is most probable that the Dorset-Somerset, the Dundry and 
the Cotteswold areas were all reconnected by a large expanse of 
water; and this is exactly borne out by the fauna.* The same 
general subsidence took place in Normandy. 
It is during the time of the Parkinsoni-zone that the 
greater number of species are found to be common to the 
various districts; and it would appear that while some species 
* This is not so much the case with Dundry as with the Dorset-Somerset 
and Cotteswold areas ; because the fauna of the Parkinsoni-zone at Dundry 
is very scanty. 
