570 Reviews—Geology of Hungerford and Newbury. 
and <Actinocamaz quadratus beds reappear in an outlier. Despite the 
occurrence of outlying patches of the Act. qguadratus Chalk near 
Kintbury and Winterbourne, the tendency of the Eocene to overstep 
the higher zones of the Chalk towards the north is clearly recognisable. 
This northward overstep of the higher parts of the Chalk may, the 
author thinks, safely be attributed to an early Tertiary or pre- 
Tertiary planation, after the Chalk had received a gentle tilt 
approximately towards the south, and he considers that the northward 
overstep of the higher zones of the Chalk by the Eocene formation, 
which he has shown to exist in this district, is not merely a local 
phenomenon, but part of the transgression which cuts out the 
Belemnitella mucronata zone to the north of Salisbury and the greater 
part of the Actinocamax quadratus zone somewhere between that place 
and the crest of the Sydmonton range. 
From the evidence before him the author infers that at or a little 
after the close of the Cretaceous period the tract, now the western 
half of the London Basin, formed part of the northern slope of an area 
of relative depression whose centre or axis lay far to the south, 
possibly on the site of the English Channel, and that before the 
deposition of the earliest Eocene sediments so far recognised in this 
region, the gently-inclined Chalk was subjected to a planation 
which bevelled off its higher zones in descending order towards 
the north, leaving here and there a troughed outlier such as that at 
Kintbury. The Eocene beds thus rest upon an eroded surface of 
Chalk, and the author considers that, at least, the ultimate shaping 
of this platform was the work of the sea. He describes the junction 
as even, or at most but shghtly undulating, except, of course, where 
the Chalk has been indented by piping in more recent times. The 
top of the Chalk is often penetrated by tubular borings filled by 
material similar to that of the Eocene bottom bed. Similar borings in 
the top of the Chalk have been recorded in the adjoining districts, and 
have been variously referred to boring molluscs and to the roots of 
marine plants.' 
The bottom bed of the Eocene consists of a few feet of dark-green 
or speckled greyish-green glauconitic loamy sand interbedded with 
seams of grey, greenish, or brown clay, often roughly laminated. 
Slightly worn or pitted flint nodules, with green coats and pebbles, and 
subangular chips of flint with the same external coloration are 
almost invariably present at the base, the nodules usually appearing 
in section as a single row at, or a few inches above, the top of the 
Chalk. Concretions of iron oxide, small granular aggregates of ‘ race,’ 
and fine seams of chalky material are not uncommon in the same 
position, and in some places these and derived chalk fossils are 
abundant. 
It is, we think, usually believed that the green-coated flints so 
frequently found at the bottom of Eocene beds where they rest upon 
Chalk are a part of the insoluble residue left by the underground 
1 See W. Whitaker, ‘‘Geology of the London Basin’?: Mem. Geol. Surv. 
(1872), p. 100. W. H. Hudleston, ‘‘Excursion to Reading’: Proce. Geol. 
Assoc., vol. iv (1876), p. 521. 
