Yol. 52.] IN YORKSHIRE AND LINCOLNSHIRE. 191 



The sum of the available evidence regarding the inland extension 

 of the Speeton Series in Yorkshire indicates, therefore, that these 

 rocks undergo a rapid attenuation as a whole in a westerly direc- 

 tion, and that all disappear within 14 miles of the coast except the 

 uppermost division (Belemnites minimus-meals : Zone A), which 

 persists as the pebbly or clayey basement-layer of the Ked Chalk, 

 swelling locally into a thicker deposit of ferruginous sand akin 

 to the Lincolnshire Carstone. 



The data are insufficient to prove whether the Lower Cretaceous 

 Clays end off against the edge of their basin of deposition, and are 

 simply overstepped by the Upper Cretaceous strata ; or whether 

 a true unconformability, as in so many other parts of the country, 

 is developed in them at this horizon. That erosion took place in 

 the western part of the district before the deposition of the Red 

 Chalk is indeed certain ; but it is not certain that the clays of the 

 coast-section ever extended so far westward. 



IV. Tee Speeton Series in Lincolnshire. 



a. General Observations and Bibliography. 



With respect to the Lincolnshire sections my present purpose has 

 regard for the sequence of the rocks rather than for their local 

 stratigraphy ; and as the whole area has been recently examined and 

 reported upon by the officers of the Geological Survey, whose maps 

 and memoirs * afford all the necessary information bearing on the 

 mode of occurrence and extent of the various strata to be considered, 

 it will be neither requisite nor desirable that I should reiterate 

 such details. My aim therefore will be to give the broader out- 

 lines only of the general stratigraphy, but to enter more fully into 

 the palaeontological and other evidence which may afford the means 

 for the correlation of the rocks in question with the more easily 

 classified clays of the Speeton section. And indeed, though during 

 the course of my field-work in this area I have gone repeatedly 

 over the whole extent of the Lower Cretaceous outcrop, I have 

 concentrated my attention chiefly on such places as promised the 

 best palaeontological results. The most suitable localities for this 

 purpose have proved to be the broken escarpment near Acre 

 House, with its abandoned iron-ore workings ; the limestone-pits of 

 Normanby, Walesby, Tealby, and Willingham ; the fine railway- 

 cutting sections on either side of Donnington-upon-Bain ; and the 

 brickyards and sand- and sandstone-pits of the Spilsby district. 



Of the palaeontological material collected only a small portion can 

 be adequately dealt with at present, but fortunately the cephalo- 

 poda are sufficiently abundant and characteristic to allow of definite 



1 Sheets (one inch) Nos. 86, 84, and 83. Memoirs, ' North Lincolnshire and 

 South Yorkshire' (Sheet 86); 'Country around Lincoln' (Sheet 83); and 

 * East Lincolnshire ' (Sheet 84). 



