CRETACEOTIS SERIES IN LINCOLNSHIRE AND YORKSHIRE. 363 



from some cause or other during or after deposition, the base of this 

 division assumes characters differing entirely from its usual appear- 

 ance, and that the gritty chalk above is at the horizon of the 

 Inoceramtis-bed . 



But, again, we have an analogy in Norfolk, and, as before, reversed; 

 there the base of the Chalk Marl becomes harder, more calcareous, 

 and its central part more gritty as it thins to the northward, and 

 the Sponge- and Inoceramus-beds are found as the condensed equiva- 

 lents of these portions of it ; in Yorkshire both these beds appear to 

 be losing much of their distinguishing characters, and are being 

 absorbed, as it were, in the thickening Chalk Marl. 



Notwithstanding the fact of invasion by mud-bearing currents, 

 the deposition of the Eed Chalk and Chalk Marl must have continued 

 at Speetou without interruption; there is no break, no evidence of 

 variation in the direction or strength of current-action, and therefore 

 no bed such as the Cambridge Greensand or the Chloritic Marl 

 which can be taken as the line of separation between these divisions. 



The Grey Beds. — The courses of grey-coloured chalk which I 

 recognize in Lincolnshire as the equivalent of the Totternhoe Stone 

 determine the upper limit of the Chalk Marl. I use the term 

 ** Grey Bed " in preference to Totternhoe Stone, because I found the 

 courses referred to known and recognized by that name in Lincoln- 

 shire. Although well marked by its fauna and lithological characters, 

 it is by no means so important a bed, except for stratigraphical 

 purposes, as the Totternhoe Stone, and the name would lead to a 

 higher estimation of it than is due. The persistence of so thin a 

 bed and its fauna so far north is remarkable, and, though it seems to 

 be dying out, it is quite recognizable at Speeton. 



The Grey Chalk. — "With such marked variations in thickness as 

 occur in the Red Chalk and Chalk Marl, it is remarkable to find 

 that the variation in the thickness of this division over the whole 

 area included in this paper is only a few feet. 



It has been shown that, as we proceed northward, certain 

 lithological characters, which first begin to manifest themselves in 

 the marly bands just above the Totternhoe Stone in Norfolk, become 

 greatly developed in South Lincolnshire ; and throughout this county 

 and Yorkshire the base of the Grey Chalk is usually of a marly 

 nature. This fact serves to confirm the correctness of my reading 

 of the sequence of the Lower Beds of the Upper Cretaceous series in 

 Lincolnshire and Yorkshire. 



At Speeton the circumstances of its weathering bring the nature 

 of this part of the Grey Chalk into strong relief. There, however, 

 it seems to be nodular and much like bed 3. 



The Belemnite-Marls. — The occurrence of Belemnitella plena in the 

 band of variegated marl some 14 feet or 15 feet below the flints in Lin- 

 colnshire confirms the correlation suggested by Mr. Jukes-Browne *, 

 viz. that these marls are the representatives of the Belemnite- 

 marls of Hertfordshire, Cambridge, &c. The band of bluish-black 

 clayey material in which I found the Belemnite at Barton-cn- 

 * " Geol. of part of East Lincolnshire," Mem. Geol. Survey, p. 29. 



