Tol. 52.] IN YORKSHIRE AND LINCOLNSHIRE. 193 



The scheme first proposed by Pavlow in 1889, after his pre- 

 liminary study of the fossils of the deposits, and afterwards more 

 fully stated and slightly amended in 1891-92, is substantially that 

 which I brought before the British Association in 1890, and repro- 

 duced in ' Argiles de Speeton et leurs Equivalents ' in 1891 ; and 

 between this and the propositions of the previous workers there are 

 radical differences. 1 Further investigation has fully confirmed the 

 correlation suggested by Pavlow and myself, and it is now sought 

 to place on record the field-evidence, not heretofore published, by 

 which the comparison is sustained. Amid the general discussion 

 of this evidence some side-issues will be debated which are of much 

 consequence to the right understanding of the relations of the series 

 as a whole. The deposits will be considered in their upward 

 stratigraphical sequence. 



b. The Kimeridge Clay. 



In comparing the Yorkshire and Lincolnshire areas we possess in 

 the Kimeridge Clay an admirable base-line. 



Though, owing to the crushed condition of the fossils in both 

 districts, the list of recognizable species in common is short, the 

 general similarity in position and composition is so close that no 

 reasonable doubt can exist that the bituminous shales 2 which 

 underlie the Spilsby Sandstone everywhere to the southward of 

 Caistor in Lincolnshire are the equivalents of the similar shales 

 (Zone E) underlying the ' Coprolite-bed ' (Zone E) of the Speeton 

 section, and were laid down in the same basin of deposition. 



It is indeed possible that the uppermost portion of this deposit 

 may have been locally removed by erosion in certain areas in Lin- 

 colnshire previous to the deposition of the Spilsby Sandstone, since 

 the researches of the Geological Survey have gone to show that 

 there is a definite unconformable overlap of that rock in the 

 northern part of the county ; 3 and the absence, so far as is yet 

 known, of the large belemnites of the Oivenii-gYonp (Belemnites 

 magnificus, Puzosi, etc.), which occur at Speeton at the top of the 

 bituminous shales, may perhaps be thus accounted for. These 

 fossils are, however, by no means common even in the shore-expo- 

 sures at Speeton, and it may well be that their apparent absence 

 in Lincolnshire arises only from the lack of good collecting-ground 

 at this horizon. 



1 With respect to the Geological Survey publications, it is to be noted that 

 the Lincolnshire deposits containing Belemnites lateralis are fully described 

 in the recently-published Mem. Geol. Surv., 'The Jurassic Rocks of Great 

 Britain,' vol. v. (pp. 286 et seqg.), and the corresponding portion of the Speeton 

 Clay in vol. i. (Yorkshire) of the same series, and this seems to imply an 

 acceptance of the views of Prof. Pavlow respecting their age, though no 

 very definite opinion is in either case expressed. See second division of 

 Table of comparisons. 



2 For further information regarding the Kimeridge Clay, see J. F. Blake, 

 ^uart. Journ. Geol. Soc. vol. xxxi. (1875) pp. 196-233; T. Roberts, ibid. 

 vol. xlv. (1889) pp. 545-560, and Geol. Surv. Mems., yam cit. 



3 Mem. Geol. Surv. 1888, • The Country around Lincoln ' (Sheet 83), p. 82. 



