98 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. (Dee. 8, 
of the fact of all but one of the 19 peculiar and mostly exclusively 
Arctic forms of Bridlington being absent from the Lower and Middle 
Glacial, that of these 72 forms no less than 46 do not occur at 
Bridlington ; and even yet more striking is it that, of this 46, only 
1 is exclusively Arctic. 
I may add that the difference in latitude between Bridlington 
and these Lower and Middle Glacial shell-localities does not exceed 
one degree*, and that the actual distance between them and Brid- 
lington is from 100 to 120 miles. 
I defer any remarks upon the striking, Crag-like, and seemingly 
southern facies of the Middle-Glacial fauna, because I expect to add 
materially to the number of that fauna, and because it will be 
more advantageously considered when describing the structure of 
the Lower and Middle Glacial formations. 
We see however, that, as the evidence at present stands, the fauna 
yet obtained from the Lower and Middle Glacial deposits (especially 
that from the latter) presents almost as much dissimilarity to the 
Bridlington fauna as the mollusca of the German Ocean do to those 
of the Greenland and Spitzbergen seas; so that no grounds exist 
for identifying, upon paleontological evidence, those Glacial beds of 
the Eastern Counties which are inferior to the great chalky clay, and 
whose structure and physical relationship to the Crag we have the 
advantage of studying in immediate contiguity to the Crag itself, 
with any of the Glacial series of Yorkshire, but, on the contrary, 
that the paleontological evidence points to their complete distine- 
tion. The uppermost of the Hast-Anglian series, the great chalky 
clay, with which Mr. Rome and myself identified the basement- 
clay of Holderness (a), has never yielded any other than derivative 
fossils; but this basement clay at Dimlington cliff, teeming with 
chalk (a), has, near to its junction with the base of the purple 
clay (c), lately yielded Sir Charles Lyell a few forms of mol- 
lusca which, he informs me, he regards, as far as they go, as 
resembling those of the Bridlington bed. The position of the base 
of Dimlington cliff, whence Sir Charles obtained these, is indi- 
cated, according to my view of the case, in the vertical section, the 
basement-clay from which these shells came appearing, from adja- 
cent borings, to descend upwards of 100 feet below the base of the 
cliff. 
I now propose to examine, on physical grounds, what part of the 
Yorkshire clay may, and what may not, be regarded as identical 
with the uppermost or great chalky member of the East-Anglian 
series. 
The absence of chalk débris in the clay lying to the north of the 
Wolds seems to have been regarded by geologists as evidence of a 
drift from north to south, though the hypothesis never appears to 
have been brought to the test of critical examination until Mr. 
Rome and I, in our quoted paper, cursorily endeavoured to refute 
it. Nor do geologists ever appear to have noticed the fact, so con- 
* In the case, however, of one shell, Ostrea edulis, obtained only at Stevenage, 
the difference in the latitude is nearly two degrees. 
