CHEAT OOLITE SERIES : HIBALDSTOW. 429 
Corbicella. 
Lima rigida. 
Modiola furcata. 
imbricata. 
Myacites calceiformis. 
Pteroperna plana. 
Trigonia costata. 
flecta. * 
striata. 
Rhynchonella concinna. 
Ostrea Sowerbyi. 
Mr. Usshe 1 ' remarks that from Hibaidstow northward there is 
no surface-indication of the extension of the Great Oolite Lime- 
stone, though it may be represented by 1 1 feet 7 inches of rock 
and shale in the boring at Brigg. Thus the Great Oolite Lime- 
stone dies away, apparently interdigitating with clays, and finally 
permitting of the direct superposition of beds having the 
character of the Great Oolite Clay upon the Upper Estuarine 
Series.* 
Near Lincoln the Great Oolite Clay is from 20 to 26 feet thick. 
It consists of dark bluish -grey clay often mottled with green, and 
contains numerous shells of Ostrea Sowerbyi, O.^rcgaria, and also 
Rhynchonella concinna, which appear to be most abundant in the 
upper part, at the junction with the Cornbrnsh.t The clay was 
formerly dug for brickmaking near Metheringham station, but 
now there are very few sections worthy of note along the 
outcrop that extends towards Brigg. 
Mr. Ussher has stated that the thickness of the Great Oolite 
Clay may be from 20 to 30 feet near Gander Hill, south-east of 
Hibaldstow. He notes that from Low Bank to Brigg the clay is 
concealed by Alluvium. It is proved at Brigg ; but from Brigg 
northwards it is concealed by Alluvium and Sand for a distance 
of nearly 3 miles. The thickness of the Clay would appear to be 
24 feet 4 inches in the Brigg Boring, and it was- encountered at a 
depth of 105 feet from the surface. On the east of Thornholme 
Priory and near Broughton Carr Side, green and blue clay, with 
Ostrea, was visible. 
Referring generally to the clays between the Lincolnshire 
Limestone and Cornbrash in North Lincolnshire, the Kev. J. E. 
Cross estimated their thickness at 40 feet; and he gave the 
following list of fossils from the beds : 
Fish-remains. 
Gervillia crassicosta. 
Modiola ungulata. 
Ostrea subrugulosa. . 
Perna rugosa, var. quadrata. 
Triffonia flecta. 
Ostrea Sowerbyi. 
Mr. Ussher states that Cornbrash forms the surface for about 
a quarter of a mile 'west of Appleby Station; its junction with 
the Great Oolite Clay was shown in a pit on the south side of the 
Hail way. J 
The divisions of Upper Estuarine Series, Great Oolite Lime- 
stone, and Great Oolite Clay appear to be continuous as far as 
Hibaldstow. At Thornholme Priory and Mickle Holme, north 
of Appleby, clay alone occupies the interval between the Inferior 
Oolite and the Cornbrash. Mr. Ussher states that this clayey 
series "is about the same thickness as the Great Oolite Clay, 
* Geol. 'N. Lincolnshire, pp. 82-84. 
f Geol. Lincoln, p. 68 ; Geol. N. Lincolnshire, p. 85. 
% Geol. N. Lincoln, pp. 85, 86 ; Cross, Quart. Joum. Geol. Soc., vol. xxxi. p. 125. 
