818 STRATIGRAPHICAL GEOLOGY. — [Boox VI. 
of Britain are perhaps merely fragments. The Wealden beds are suc- 
ceeded. conformably by the group of arenaceous strata which have long 
- been known under the awkward name of ‘‘ Lower Greensand.” They 
consist mainly of yellow, grey, white, and green sands, but include also 
beds of clay and bands of limestone and ironstone. They have been sub- 
~ divided in descending order as under : 
Folkestone beds . , ; j k 2 ‘ : - 70 to 100 feet 
Sandgate beds . ; : . : 5 . «a> dD pop mnt 
Hythe beds ; : ; : : ; 5 4 80, 200s, 
Atherfield Clay resting on Wealden . : 3 . 20" oom 
These strata represent the Upper Neocomian series of the Continent. 
Among their fossils the following may be mentioned: Towaster com- 
planatus, Rhynchonella gibbsiana, Terebratula sella, Hxogyra sinuata, Ger- 
villia anceps, Ostrea frons (carinata), Pecten quinquecostatus, Perna Mulletit, 
Arca Raulini, Panopea plicata, Trigonia aleformis, Ammonites Deshayesii, 
Ancyloceras gigas, Nautilus radiatus. Of the total number of fossils from 
the ‘“ Lower Greensand” or Upper Neocomian, about 300 in number, only 
18 or 20 per cent. pass up into the Upper Cretaceous. This marked palzeon- 
tological break, taken in connection with an unconformability between 
the ‘‘ Lower Greensand” and Gault in the southern counties, and be- 
tween the top of the Speeton clay and the overlying Hunstanton lime- 
stone in the north, shows that a definite boundary-line can. be drawn 
between the lower and upper parts of the Cretaceous system in England. 
Uprver Creraceous.—Three leading lithological groups have long been 
recognized as constituting the Upper Cretaceous series of England. First, 
a band of clay termed the Gault; second, a variable and inconstant 
eroup of sands and sandstones called the “‘ Upper Greensand ;” and third, 
a massive calcareous formation chiefly composed of white chalk. But 
the foreign nomenclature, founded mainly on paleontological considera- 
tions, and given in the foregoing table (p. 815), may now be adopted, 
as it brings the English Upper Cretaceous groups into recognizable 
parallelism with their continental equivalents. | 
Gault.—aA dark stiff blue, sometimes sandy or calcareous, clay with 
Jayers of pyritous and phosphatic nodules and occasional seams of green 
sand. It varies from 100 to more than 200 feet in thickness, forming a 
marked line of boundary between the upper and lower Cretaceous rocks, 
overlapping the latter and resting sometimes even on the Kimmeridge 
clay. One of the best sections is that of Copt Point on the coast near 
Folkestone, where the following subdivisions have been established by 
Messrs. De Rance and Price :! 
Upper Greensand. 
(11. Pale grey marl clay (56ft. 3in.), characterized by Ammonites rostratus 
(inflatus), A. Goodhalli, Ostrea frons, Inoceramus Crispii. 
10. Hard pale marly clay (5ft. lin.), with Kingena lima, Rostellaria 
maxima, Plicatula pectinoides, Pecten raulinianus, Pentacrinus Fit- 
toni, Cidaris gaultina. 
9. Pale grey marly clay (9ft. 44in.), with Inoceramus sulcatus, Ammonites 
pare Pholadomya fabrina, Plewrotomaria Gibbsii, Scaphites 
Vqual7s, 
8. Darker clay with two lines of nodules and rolled fossils (94in.), with 
Ammonites cristatus, A. Beudanti, Pholas sancte-crucis, Mytilus 
{ Gallicnnei, Cucullea glabra, Cyprina quadrata. 
Upper Gault. 
———_----—— 
' ©. KH. De Rance, Geol. Mag. y. p. 163; F. G. H. Price, Q. J. Geol. Soc. xxx. p. 342. 
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