154 L. Dudley Stamp— 
certainly a continuation of the Sables de Bracheux (zone of Cyprina 
scutellaria). This was recognized also by Prestwich. About 33 feet 
thick at Newhaven, it is generally hidden by slips at Whitecliff Bay, 
and’ has decreased to about 4 feet at Alum Bay. The enormous 
marine transgression which took place at the time of formation of the 
Bracheux Sands has been pointed out above. Here, in the Hampshire 
Basin, the evidence for the transgression is equally well marked, and 
also the rapid fillmg up of the shallow sea with fluviatile and 
estuarine deposits. 
Y presian.—The marine invasion of Ypresian times in England was 
one of the most extensive of all the Hocene invasions, yet the uncon- 
formity is very slight. As White! has pointed out, the estuarine 
and freshwater flats of late Landenian times favoured a rapid yet 
tranquil marine invasion. The conditions for the existence of the 
mixed Blackheath fauna of the London Basin did not exist in the 
Hampshire Basin, i.e. the brackish-water lagoon phase of the 
Landenian only occurs to the extreme east, at Newhaven, etc. 
The region was too far from the Wealden uplift to receive great 
masses of pebbles such as one finds in the London Basin, hence 
the Blackheath Beds are absent. The mass of the London Clay 
commences with a thin sandy pebble-bed—the Basement Bed. 
The London Clay itself is generally somewhat sandy, especially 
in the west. It thickens steadily from west to east, from 80 to 
100 feet at Studland Bay, 233 feet at Alum Bay, and 320 at 
Whitecliff Bay, to 340 feet at Portsmouth. It includes some beds 
of fine sand in the upper part and passes up quite gradually into the 
fluviatile Bagshot Sands. As one would expect from their being 
continental deposits, the latter are very thick in the west, estimated 
at over 500 feet near Bournemouth, and they become thinner 
eastward, and are only about 100 feet thick in Whitecliff Bay and 
30 feet at Portsmouth. To the north of Bracklesham Bay they are 
represented by a thin bed of sand a few feet in thickness between the 
marine deposits of the London Clay and Bracklesham Beds. The 
great mass of sands grouped under the term Bagshot Sands in the 
Alum Bay section undoubtedly include representatives of the 
Bracklesham Beds—both Lutetian and Ledian. The sands are 
decalcified and unfossiliferous, but it is hoped that a mineralogical 
examination of the sands may lead to a detection of glauconite, and 
indicate the marine origin of certain of the beds. The marine 
invasions of Lutetian and Ledian times are both very clearly seen 
in the Whitecliff Bay section, and are traceable as the Bournemouth 
Marine Series and the Hengistbury Head Beds respectively in the 
Bournemouth Bay section, hence they must be represented in 
Alum Bay. 
The London Clay in the neighbourhood of Portsmouth—so ably 
studied by Meyer 2—exhibits several interesting features. There 
1 White, op. cit., 1915, p. 11. 
2 Meyer, “‘ On the Lower Tertiary Deposits recently exposed at Portsmouth ”’: 
Quart. Journ. Geol. Soc., vol. xxvii, 1871, p. 74. 
