380 ME. H. HOME ON AMPTHILL CLAY IN [Aug. I903, 



to one of the Ampthill-Clay oysters exhibited on the table. This 

 was a specimen referred to Prof. Seeley's Ostrea discoidea, which, 

 according to the late Thomas Roberts, is the only fossil known to 

 be entirely restricted to the Ampthill Clay. The speaker said that 

 while Prof. Seeley had many years ago intended to describe this form, 

 no description, so far as he was aware, had yet been published, 

 though the name had still remained in use. A very imperfect text- 

 figure which had appeared in a Geological-Survey Memoir did not 

 suffice to raise this above the level of a manuscript name. 



Referring to the previous speaker's suggestion, that the mass of 

 Jurassic clay described by the Author might possibly prove to have 

 been derived from the lowest part of the Kimmeridge Clay, the 

 speaker said he was not aware that Cardioceras eoccavatum had ever 

 been known to occur in the base of the Kimmeridge Clay. 



Mr. E. A. Martin asked what was the direction of the angle of 

 dip of the septaria in the mass of Ampthill Clay, and whether it 

 was observed to differ from the direction of the dip of similar 

 layers in the nearest position in situ of the same clay. He 

 also wished to take the opportunity of asking whether the old 

 woodcuts, which had seen so much service in the Memoirs of the 

 Geological Survey, could not be replaced by other and more modern 

 methods of illustration. They were not creditable to present-day 

 science. 



Mr. Whitaker spoke of the advantage of engineers possessing a 

 knowledge of geology, and congratulated the Society on having 

 such work as the Author's brought before it. So far as the paper 

 was concerned, it did not matter whether the boulder was of 

 Ampthill or of Kimmeridge Clay ; the point was that it was a 

 true boulder. 



Mr. R. S. Herries alluded to the large boulder, or series of 

 boulders, of Lower Lias in the middle of Filey Bay, mentioned by 

 Mr. Lamplugh in a note to his paper on the Speeton Clay in 1889. 

 These blue clays occur mixed up with the Boulder-Clay, both in the 

 cliff and on the foreshore, for a quarter of a mile or more, and are 

 full of fossils belonging to the Ai-matus-zone of the Lower Lias, 

 the nearest exposure of which is on the south side of Robin 

 Hood's Bay, 20 miles to the north. The character of the fossils 

 exhibited by the Author seemed to be as much Kimmeridgian as 

 Corallian. 



Prof. Watts regretted that all the various schools of glaciology 

 were not represented at the discussion of a paper of this kind. 

 The mechanism by which the transporting work was done was the 

 crux of the problem. It was noticeable that Chalk was absent in 

 the lea of the Wash, unless it could be identified as forming the 

 big boulders distributed about that region. In regard to the Great 

 Chalky Boulder-Clay, the possible agency of the Scandinavian ice- 

 sheet must be borne in mind when seeking for an explanation of its 

 occurrence. 



The Chairman (Sir Archibald Geikie), in summing up the 

 discussion, remarked that the paper to which they had listened 



