64 
PLASTIC CLAV. 
exuviae occur in this division, or in the lowermost 
bed of clay, upon the chalk itself, we may con- 
clude that the inferior or freshwater deposits are 
wanting, and that the ujipermost division reposes 
immediately upon the chalk. Such appears to be 
the case at Castle Hill ; and we must therefore 
refer the lignite, red marl with vegetable remains, 
and the few freshwater shells whicii accompany 
them, to the middle of the series ; and the clay, 
with cerithia and other marine shells that form 
so large a proportion of the cliff, to the upper 
division ; the lowermost bed of the French series, 
the pure argille plastique, being absent. In the 
London clay at Bracklesham (the Premier terrain 
marin of M. Cuvier and Brongniart), a more 
striking analogy with the corresponding strata in 
France is observable ; and the fossils are identical 
with those of the Calcaire grassier of the environs 
of Paris. 
On the opposite coast of France, strata cor- 
responding with those of Castle Hill, and Chimting 
Castle, occupy the same relative position. 
In the perpendicular cliffs, under the light- 
house of St. Margaret, to the west of Dieppe, the 
following beds occur : — 
1. Chalk. 
2. Sand and sandstone in thick beds, containing 
concretions of tlie same substances. 
3. Plastic clay, impure, and containing lignite 
much charged with pyrites. Also oysters, cerithia, 
&c., both in beds, and irregularly disseminated. 
4. Alluvium. 
These dejiositsM. Brongniart considers as identical 
