362 MR. W. HILL ON THE LOAVER BEDS OF THE UPPER 



of the Inoceraynits-hedi of Hunstanton througliout the area above 

 mentioned. 



The remainder of the Chalk Marl, though seamed by well-marked 

 marly bands and of a somewhat rongh and nodular character, con- 

 tinues without much variation as a hard, whitish, and purely cal- 

 careous deposit, similar to that of ^orth-west Norfolk. As in the 

 case of the Red Chalk, there is an increase in its thickness from 18 

 feet at Huustanton to 32 feet at the southern end of the Lincoln- 

 shire Wolds ; this it probablj^ maintains through the county. At 

 the north-west extremity of the Yorkshire Wolds it becomes some 

 8 feet less in thickness, probably from the same cause to which the 

 attenuation of the Eed Chalk may be referred. From Wharram 

 along the northern escarpment of the Yorkshire Wolds so little 

 evidence of the sequence of the beds above the Eed Chalk can be 

 obtained that it is somewhat puzzling to find that the thickness of 

 the Chalk Marl has increased from 25 feet at Leavening to 77 feet 

 at Speeton, that the well-marked divisions above the Eed Chalk 

 of Sponge- and Inoceramus-\)eds are gone, and that lithologically, as 

 microscopical and chemical evidence prove, there is a complete 

 passage from the Gault to the Chalk Marl. Sympathy of the mind 

 with the eye must be the reason that the division-line is taken at 

 the top of the coloured material ; except for this peculiarity, the 

 change from Eed Chalk to bed 2 would appear to be gradual. The 

 Belemnite so characteristic of the Eed Chalk continues to occur at 

 least halfway through the bluish-grey material of bed 2, which I 

 take as the basement-bed of the Chalk Marl, though this fact has 

 its parallel in the occurrence of the same Belemnite in the base of 

 the " Sponge-bed " in Norfolk. 



The colour, nodular character, and marked marly bands of beds 

 2 and 3 are, except at Speeton above the " Grey Bed," without a 

 parallel in the English Chalk. The chemical analysis of bed 2 shows 

 that it contains siliceous matter in proportions comparable with parts 

 of the Chalk Marl near Cambridge ; but it passes up to a purely 

 calcareous deposit in bed 3. Although in its 28 feet of thickness 

 this bed shows some variation of structure, it may be compared 

 generally with the Chalk Marl of the north, and with the base of it 

 at Eoydon or Shouldham in Norfolk. 



In Bedfordshire and Norfolk the bed overlying the Gault is 

 invariably marked by the abundance of Avicula grypliceoides. At 

 Speeton this fossil occurs commonly in bed 2 and is abundant in the 

 base of bed 3, towards the upper part of which it gradually dis- 

 appears. 



Near the top of bed 3 there is an increase in the quantity of 

 shelly fragments in the Chalk, and this is especially noticeable in the 

 marly bands and veins. In a specimen from these, I found the only 

 glauconite-grains I have seen in the Speeton Chalk. This grittiness 

 passes away upward, and the material assumes the normal aspect of 

 northern CJaalk Marl. 



The above evidence leads me to conclude that bed 2 and the lower 

 two thirds of bed 3 are the equivalent of the " Sponge-bed," although, 



