148 L. Dudley Stamp— 
maps, showing the distribution of the various marine Kocene beds 
in the Paris and Belgian regions; and the map showing the 
distribution of the zones of the Landenian demonstrates very clearly 
the successive overstep in all directions. 
The Upper Landenian (the so-called Sparnacian) marks a silting up 
of these shallow seas. Broad, shallow lagoons teeming with estuarine 
molluscs existed over a very large part of the great basin, and in 
them were deposited sediments of the type of our Woolwich Beds. 
Round them there is the broad band of lacustrine and fluviatile 
deposits of Reading type. The Upper Landenian was the most 
extensive, geographically, of all the continental episodes. The extent 
of marine waters in the centre of the basin must have been very 
small indeed. Almost the only locality now remaining where the 
whole of the Landenian is marine is the Isle of Thanet. 
The marine Landenian has been called Thanetian on the 
supposition that it corresponded to the Thanet Sands of the London 
Basin. As Prestwich? and others have pointed out, the zone of 
Cyprina scutellarva is represented in England by the Bottom Bed of 
the Woolwich Series. The author has recently adduced further proof 
of this correlation.? The name Thanetian must therefore be 
dropped. It follows also that the “ Sparnacian”’ deposits of the 
French do not correspond exactly to our Woolwich and Reading 
Beds. 
Y presian.—When one remembers the very large area covered by 
the shallow lagoons of Upper Landenian times, it is clear that even 
a slight disturbance would cause a very great change in the 
distribution of land and water. This question has been dealt with at 
some length elsewhere,‘ and it is sufficient to note here one or two of 
the more important ‘conclusions. The waters of the invading 
Ypresian sea flooded very rapidly over the Upper Landenian lagoons. 
There are extensive accumulations of well-rolled flint-pebbles, and 
elsewhere very fine or well-washed sands, showing the disturbed 
conditions which prevailed at the time. For a short time the 
incoming marine fauna lived side by side with the existing fauna of 
the lagoons, and one gets the curious mixed fauna of the Sables de 
Sinceny. These basal Ypresian beds compare very closely with 
their equivalents in England—the Blackheath Beds. It is interesting 
to note that this distinctive fauna, associated with the peculiar type 
of lithology of the beds (that is beds of unbleached, well-rounded 
flint-pebbles), is restricted in geographical distribution to areas of 
pre-existing estuarine lagoons. Where the Ypresian sea invaded 
1 Leriche, Bull. Soc. géol. France, sér. Iv, vol. xii, 1912, pls. xxiii-xxvii. 
2 Prestwich, Quart. Journ. Geol. Soc., vol. xliv, 1888, pp. 98-9. 
3 Stamp and Priest, ‘‘ Geology of the Swanscombe Eocene Outlier’: Proc. 
Geol. Assoc., vol. xxxi, 1920, p. 187. 
4 Stamp, ““ On the Beds at the Base of the Ypresian in the Anglo-Franco- 
Belgian Basin ’’: read at the meeting of the Geologists’ Association, July 2, 
1920. Guo. Maa., Vol. LVII, 1920, p. 380 (in the Press). - 
