~ 
Parr IV. Scr. i. § 2.] ‘EOCENE. 845 
ences in lithological and paleontological characters serve to indicate the 
geographical features of the south-east of England at the time of deposit, 
showing in particular that the sea of the Thanet Beds had gradually 
shallowed, and that an estuary now partly extended over its site. The 
organic remains as yet obtained from this group amount to more than 
100 species. They include a few plants of terrestrial growth, such as 
Ficus Forbesi, Grevillea Heeri, and Laurus Hookeri—a flora which, contain- 
ing some apparently persistent types, has a temperate facies! The 
lamellibranchs are partly estuarine or fresh-water, partly marine ; 
characteristic species being Cyrena cuneiformis and C. tellinella. Ostrea 
bellovacina forms a thick oyster-bed at the base of the series. Ostrea 
tenera is likewise abundant. ‘The gasteropods include a similar mixture 
of marine with fluviatile species (Cerithium funatum (variabile), Melania 
inquinata, Melanopsis buccinoides, Neritina globulus, Natica subdepressa, Fusus 
latus, Paludina lenta, Pitharella Rickmanni, &c.). The fish are chiefly 
sharks (Lamna). Bones of turtles, scutes of crocodiles, and traces of 
birds have been found. The highest organisms are bones of mammalia, 
including the Coryphodon. 
The Oldhaven Beds,? forming the base of the London Clay, con- 
sist almost wholly of rolled flint pebbles in a sandy base, which, as 
Mr. Whitaker suggests, may have accumulated as a bank some little 
distance from shore. Though of trifling thickness (20 to 30 feet) they 
have yielded upwards of 150 species of fossils. Traces of Ficus, Cinna- 
momum, and Coniferze have been obtained from them, indicating perhaps a 
more subtropical character than the flora of the beds below, but without 
the Australian and American types which appear in so marked a manner 
in the later Hocene floras.* The organisms, however, are chiefly marine 
and partly estuarine shells, the gasteropods being particularly abundant. 
The London Clay* is a deposit of stiff brown and bluish-grey 
clay, with layers of septarian nodules of argillaceous limestone. Its 
bottom beds, commonly consisting of green and yellow sands, and rounded 
flint-pebbles, sometimes bound by a calcareous cement into hard tabular 
masses, form in the London basin a well-marked horizon. The London 
Clay is typically developed in that basin, attaining its maximum thick- 
ness (500 feet) in the south of Essex. Its representative in the Hamp- 
shire basin is known as the “ Bognor Beds,” but these strata differ 
somewhat both lithologically and paleontologically from the typical 
“development. The London Clay has yielded a long and varied suite of 
organic remains, from which we can see that it must have been laid 
down in the sea beyond the mouth of a large estuary, into which abun- 
dant relics of the vegetation, and even sometimes of the fauna of the 
adjacent land, were swept. According to Prof. T. Rupert Jones the 
depth of the sea, as indicated by the foraminifera of the deposit, may 
have been about 600 feet. Professor Prestwich has pointed out that 
there are traces of the existence of paleontological zones in the clay, the 
lowest zone indicating in the east of the area of deposit a maximum 
depth of water, while a progressive shallowing is shown by three higher 
1 J. S. Gardner, “ British Eocene Flora,” Palzontog. Soc. p. 29. 
* Whitaker, Q. J. Geol. Soc. xxii. (1866), p. 412; Geology of London, p. 239. 
3 J. 8. Gardner, Op. cit. pp. 2, 10. 
* Prestwich, Q. J. Geol. Soc. vi. p. 255; x. p. 485. Whitaker, Geology of London, 
p. 273. 
