xi MOLLUSCA OF SOMERSET. 
in the northern half of the county. There is much rugged 
land with beautiful scenery in the eastern parts around Pensel- 
wood. 
Summarising briefly the geological aspects of the county, 
the Paleozoic rocks appear in the north-east (Bristol and 
Radstock coalfields), and in the west (Quantocks and Exmoor), 
the hollow between them is filled with Mesozoic rocks. The 
Old Red sandstone appears on the Mendips, also on the banks 
of the Avon near Clifton. The Devonian formation occurs in 
the north-west corner of the county, on the Quantocks, and 
on Exmoor in the extreme west. ‘The Carboniferous limestone 
crops out between Clifton and Clevedon, and flanks the slopes 
of the Mendips; the Coal measures occur at Clapton-in- 
Gordano, Nailsea, and Radstock. The Trias appears between 
Taunton and Wiveliscombe. The Rheetic beds are largely 
exposed on the coast at Watchet, and irregularly at other 
places. The Lias occupies a large tract in the centre of the 
county, and is well seen at Street. The Oolite forms a ridge 
on the east and south-east, stretching from Bath through 
Frome to Wincanton and Henstridge. The escarpments of 
the limestones of the Lias and Oolite face the west or north- 
west, the dip being easterly. The Cretaceous rocks (chiefly 
Upper Greensand) are well developed about Penselwood in 
the east, and the Blackdown hills in the south. There are 
numerous post-Pliocene beds in the county, such are every- 
where of special interest to the conchologist, as they frequently 
contain sub-fossil shells in large numbers. The gravel, silt, 
and peat beds at Burnham, Sedgemoor, Wedmore, ete., and the 
raised beaches about Weston-super-Mare, come under this 
heading. Much of the alluvium and peat has been deposited 
since Roman times. Deposits 12ft. in depth occur at Bath 
and on the levels at Burnham. 
Valley gravel occurs along the Brue valley near Bruton, 
Castle Cary, and other places. Messrs. Santer Kennard and 
B. 3. Woodward, who examined some material from a deposit 
