J. Lamplugh — Marine Shells in Boulder-clay. 511 



subject more extensively ; and to* my further surprise found frag- 

 ments of the same shells everywhere on the coast as far north as 

 Whitby/ bej^ond which place I have not yet sought for them. And 

 it is remarkable, that wherever a double series of clays, as noticed by 

 Prof. Phillips,- can be observed, as is the case at Filey, Cayton, 

 Whitby and elsewhere, it is in the lower bed that the fragments are 

 always most plentiful and least water-worn, and this lower bed is 

 always the darker in colour, generally of a greenish tinge, and very 

 distinct from the upper bed, which is usually of a reddish brown 

 colour, north of Flamborough. This is especially noticeable in the 

 cliffs near Filey, and to the north of the last-named locality there 

 exist, between the two clays, traces of a bed of laminated sand and 

 clay corresponding, as I believe, to the ' snuff-brown '-coloured clay 

 at Bridlington. I was only able to trace this bed for a short distance ; 

 its thickness was about two feet. 



From these facts, I think that a representative of Messrs. Wood 

 and Rome's ' Basement ' Clay wall be found to exist to the north, as 

 well as to the south of Flamborough, but on this head further in- 

 vestigation is required. 



The vast majority of the shells found in the sandy clays on the 

 South Sands at Bridlington are fragmentary. Some of these frag- 

 ments, even when found in the sandy clay, are quite water-worn 

 and rounded, but more have their angles as sharp as though newly 

 fractured, which is rarely the case with those present in the 'Purple' 

 clay. They are also more abundant in some patches than in others, 

 being generally most plentiful just below the laminated clay already 

 described. I have given below a tabular list of the species already 

 found by me both in these beds and in the 'Purple' clay, and the 

 specimens have been submitted by me to Dr. Henry Woodward for 

 more critical examination. 



That these shells are derived from the same source as those in 

 the ' Bridlington Crag ' is, I think, unquestionable ; from which it 

 follows that this ' Crag ' sand, with its numerous shells, lies in the 

 ' Basement ' or ' lead-coloured ' clay, and not in the upper ' Purple ' 

 clay, as is suggested by Messrs. Wood and Eome.^ 



There is a very strong argument in favour of this, by the un- 

 doubted presence in the ' Basement ' clay at Dimlington, further 

 south, of a similar shell-bed, which contains the same species, and is, 

 I believe, generally regarded as forming part of the same series as 

 the ' Bridlington Crag.' 



The position of the ' Crag ' furnishes us with another proof, for I 

 have myself witnessed an exposure of the upper part of the ' Base- 

 ment ' beds on the North Beach beneath Fort Hall, close to the place 

 where the ' Crag ' was first discovered. The same ' Basement ' clay 

 is again exposed on the beach about 800 yards further north, con- 

 sisting of the same dark sandy clay with many shell-fragments, and 

 overlaid, as on the South Sands, by the snuff-coloured clay. 



1 At -whicli place however tliey had become very rare. 



2 Quart. Journ. Geol. Soc. vol. xxiv. p. 254. 



3 Quart. Joum. Geol. Soc. vol. xxiv. p. 149. 



