418 MR. G. W. LAMPLUGH ON THE 



The gravels of the scries, sometimes chalky, sometimes chalkless, 

 nre arranged, as has been shown, in a kame-likc chain of mounds. 

 These beds arc occasionally coarse and morainic, bub more often, 

 are composed of line and well-strati tied material. A careful search 

 among the gravels, and especially among the finer chalkless gravels, 

 rarely fails to reveal crumb-like fragments of marine shells, or 

 even, occasionally, scattered and much-worn valves, but nowhere 

 have any organic remains been found in the beds of laminated silt, 

 warp, or clay which abound in the sections, nor in the clean sands, 

 where, if any contemporaneous fauna had existed, the remains 

 should have been preserved. The shells which occur in the gravels 

 are invariably the common species of the underlying Boulder- 

 day. 



The sections immediately north of Bridlington Quay show clearly 

 (see PI. XIII. fig. 3) that, in spite of the apparent difference, 

 these stratified beds are really equivalent to the Piirple Boulder- 

 clay, since we can trace the greater portion of the clay until it is 

 shredded out and merged with bedded loam and gravel. At the 

 same time it must be noted that this equivalence probably holds 

 good only in a general way, for the lower part of the Purple Clay 

 in the neighbouihood of Danes' Dyke seems to be merged iuto the 

 Basement Clay, and, on the other hand, the Basement Clay passes 

 up in places into the stratified beds ; and similarly the Upper Clay 

 in some of the Flamborough sections coalesces with what may be 

 considered the topmost portion of the Purple Clay, just "as it has 

 been observed to do in some sections in Holderness* and in Lin-' 

 colnshiret. But, broadly speaking, the great mass of the Purple 

 Clay may be said to resolve itself, in the Jblamborough sections, into 

 stratified deposits. 



The relationship thus existing between the Holderness and 

 riamborough-Head drifts is illustrated by the right-hand half of 

 the diagram (PI. XIII. fig. 15). 



This demonstration of the passage of the Purple Clay into the 

 Intermediate Stratified Series of Flamborough affords, 1 think, an 

 explanation of the perplexing differences between the structure of 

 the drifts on the coast-line of Holderness and in the interior. 

 While Boulder-clays nearly everywhere prevail in the clift'- sec- 

 tions, the drifts of the interior, sometimes at a distance of onlj' 

 three or four miles, consist very largely of sand and gravel, usually 

 arranged in kame-like mounds running in more or less con- 

 tinuous lines, generally nearly north and south, or otherwise 

 roughly parallel to the course of the Wolds. These, in spite of 

 certain difi'erences presently to be mentioned, I consider to belong 

 to the same system as the Gravel Eange of Plamborough Head, and 

 to have had a similar origin. 



Hamilton Hill, near Barraston, a conspicuous feature in the low 

 land within a few hundred yards of the coast, about three miles 



* Geol. Survey Mem. ' Holderness,' pp. 33-35 & 43. 



t A. J. Jukes-Browne, ' The Boulder-clava of Lincolnshire,' Quart. Joi;rn. 

 Geol. Soe. vol. xli. (1885) p. 127. 



