COLE : PHYSICAL GEOGKAPHY OF THE EAST RIDING. 119 
In the same district Oolitic rocks form a narrow band between 
the Lias and the Chalk. Two ridges are apparent, the westernmost 
consisting of a blue-hearted limestone, called Cave Oolite, and 
probably identical with the Millepore Limestone of the Coast, the 
other of Kelloways Sand Rock. At Grimthorpe and Kirby 
Underdale are outliers of Millepore, with a few Estuarine Sands. 
Thence northwards for a distance of six or seven miles we come 
across a belt of Oolitic rocks, a prolongation of the Howardian range, 
terminating at North Grimston. This area may be expected to 
yield a flora of its own. 
In the south-west corner, the Dogger, Estuarine Sandstone, 
and Millepore, or Whitwell, Limestone are exposed at Kirkham, 
Firby, Westow, and Burythorpe, whilst in the centre, by Fox Cover 
Plantation, is a mass of Kelloways rock weathered into an unproduc- 
tive bed of sand on the surface. In the south-east corner, the Lower 
Calc. Grit, resting on Oxford Clay, appears at Acklam Brow, 
Leavening, and Birdsall, with a belt of Kimeridge Clay between it 
and the Chalk, which said clay foi-ms also a triangular mass north of 
Burdsall, with its apex at Kennythorpe, and base underlying North 
Grimston Wold. In the north-west, Kenny thoipe, Langton, and 
Menethorpe are on Lower Calc. Grit, cut through in places by 
streams down to the Oxford Clay ; whilst in the north-east, North 
Grimston, Settrington, and Langton Wold present fine sections of 
CoraUian rocks. Indeed, the finest display of coral reefs in England 
is acknowledged to be at N. Grimston. Here also supra-coralline 
beds of hydraulic limestone, forming an excellent cement, are well 
developed. 
From Acklam Brow eastwards to Knapton Wold, Kimeridge 
Clay forms the sides of the Wolds, and has given rise to numerous 
landslips : indeed, this clay everywhere underlies the Chalk on the 
northern slopes of the old anticlinal ; for in Thixendale denudation 
has cut right through the Chalk, and exposed the Kimeridge Clay in 
many places. Burdale tunnel, 400ft. above sea-level, was chiefly 
excavated in this clay, which may be seen forming the sides of the 
valley up which the railway runs from N. Grimston to Burdale. At 
Huggate, however, the Chalk rests immediately on Lias, as proved 
