CEETACEOTJS SERIES IN LINCOLNSHIRE AND YORKSHIRE. 329 



occur also at Snettisham and Dersingham, but they seemed at the 

 time hardly worth recording ; their significance is now evident. 



A remarkable feature throughout Lincolnshire and Yorkshire is 

 the number of large Ammonites which occur in the basal part of 

 the Grey Chalk. 



(E.) Zone of Belemnitella plena. 



It only remains to note the bands of marl which are taken in the 

 Memoir as the upper limit of the Lower Chalk. That they are the 

 true representatives of the zone of B. plena of Hertfordshire and 

 Cambridge* is, I think, beyond doubt, for I am able to record from 

 them the typical fossil Belemnitella plena, and moreover the fossils 

 which occur in the under- and overlying chalk are such as occur at 

 the same horizon in the Midlands and the South of England, and 

 there are indications of a break at this horizon, which has been 

 discussed elsewhere t. The Belemnite-marls are seen in the Welton 

 pit as two layers of rather dark grey laminated clay separated by 

 a course of hard whitish chalk, that beneath the lower band being 

 broken and rubbly. These bands fringe the top of the pit on the 

 north side, and nothing is seen above them. 



The presence of the Marls in this pit is not noted in the Memoir, 

 the face having probably been cut back since the district was sur- 

 veyed. To their constant presence throughout the area described 

 in the Memoir I need not further allude, ample information con- 

 cerning them being given. 



To the north of this area I have seen them at Caistor, where, in 

 a pit about 3 furlongs south-east of the church, they are just seen 

 at the base ; the section is : — 



ft. 

 Soil and rubble 3 



Hard white chalk with 2 lines of flints 6 



Jointed chalk and shale f 



Hard buff and greyish chalk in even courses about 1 ft. 



thick, with partings of grey shale 11 



Zone oiBel vlena I "^^^iegated, buff and bluish-grey laminated clayey marl 



'^ \ seen for 1^ 



They are again well shown in the three large quarries west of 

 Barton on Humber. Here I had no difficulty in finding for myself 

 specimens of Belemnitella plena %, and they were evidently well 

 known by the quarrymen. 



As there is, so far as I know, no published account of the section 

 seen here, I give it as follows : — 



* Quart. Journ. Geol. Soc. vol. xlii. p. 216. 



t " Geol. of Cambridge," Mem. Geol. Survey, p. 137. 



\ Mr. E. Hall of Louth showed me the lower half of a specimen of B. plena 

 from one of the pits in which the marls occur, on the London road just south 

 of Louth. I am also indebted to Mr. Hall for specimens obtained from the 

 Grey Bed. 



