SECTIONAL TRANSACTIONS.—C. 317 
America ; but most of South America appears to have been as stable as Africa. There 
is no buckling of Australia such as would be expected if the whole continent had drifted 
far to the south-east. The northward movement of Europe and southward advance 
of Asia produced intense corrugation of narrow belts; but the structure of those 
continents indicates the moderate buckling that would be expected by great meridional 
pressure, but no great horizontal displacement. 
The biological evidence adduced by Wegener is weighty in favour of former 
connection between now separated continents, but is not in favour of the connection 
adopted by his theory. Wegener shows the former interchange of animals east and west 
across the Atlantic, but it is essential to his theory that there should have been no 
corresponding interchange across the Pacific, and that the western coast of America 
and the eastern coasts of Australia and Asia should be nearer now than at any previous 
time. Yet there is evidence of the same kind of passage across the Pacific as across the 
Atlantic. The testimony of the alligator in the Yangtse Kiang is as instructive as that 
of the manatee in the tropical Atlantic. Many groups of animals and plants have 
representatives on both sides of the southern Pacific, and are absent from the northern 
lands. These cases indicate the existence at about Oligocene times of a land or chain of 
islands across the northern Pacific. A similar land connection across the south- 
tropical Pacific is indicated by the coral islands. 
Wegener’s theory is valuable as a stimulus to discussion and as an indication of the 
more general acceptance of the mobility of the earth’s crust. But the balance of the 
evidence supports the conclusion that the great changes in the distribution of land and 
water have been due to vertical and not horizontal movements. 
Mr. W. B. Wricat, Mr. Tate Recan, F.R.S., and others. 
15. Joint Meeting of Sections C and D. Mr. M. A.C. Hivron.—The 
Pleistocene Mammalia of the British Isles and their bearing wpon 
the date of the Glacial Period. (See page 323.) 
AFTERNOON. 
16. Prof. W. W. Warts, F.R.S.—The Breidden Laccolite. 
17. Mr. T. F. Grimspate.—Ammonite Zones in Albian and Cenomanian 
Deposits of Devon and Dorset. 
Extension by the author of detailed zoning in the Albian and Cenomanian rocks, 
recently begun in this country by Dr. L. F. Spath, has produced evidence which, 
by increasing our knowledge of the stratigraphy, reveals the erroneous nature of 
certain speculations concerning the overlap of the Upper Gault [for nomenclature, see 
Spath, ‘ Report of Excursion to Folkestone,’ Proc. Geol. Assoc., 1923}. The discovery 
of Lower Gault ammonites at various localities, including Osmington [South Dorset ]— 
benettianus zone; Seaton and Lyme Regis—intermedius zone, together with the 
previously known faunas from Okeford Fitzpaine [North Dorset ]—inaequinodum 
zone; and Devizes—benettianus zone, suggests strongly that part of the Lower Gault 
was continuous beneath the Upper Gault over the whole area, rarity of fossils being 
due to the character of the rocks. 
Absence of beds IV-VIII of Folkestone is probably due to a non-sequence, com- 
parable to that proved at Dunton Green, Kent. The presence of beds X-XII is fairly 
well attested in Devon. In South Dorset the uppermost zone of the Albian has been 
traced in every exposure from Swanage to Osmington. 
Conclusions drawn from the Cenomanian are as yet mainly negative. There is no 
complete succession, the best, at Seaton, embodying three non-sequences in the Lower 
Cenomanian, while the Upper is missing. Also, most of the published records of 
ammonites are more or less unreliable. Further study, in some area where the succession 
is fuller, is needed before correlations can be established ; a few tentative suggestions 
may be advanced. 
The author wishes to express his indebtedness to Dr. Spath, for valuable assistance 
in fixing the horizons of Albian ammonites, and also for much unpublished information 
both on Albian and on Cenomanian forms. 
