216 



LOWER EOCENE STRATA OF ENGLAND. [Oh. XVL 



Fig. 215. 



MARINE SHELLS OF BRACKLESHAM BEDS. 

 Fig. 216. Fig. 217. Fig. 218. 



Pleurotoma atten- 

 iiata, Sow. 



Voluta la- 

 tretta, Lam. 



Thirritella, 



multisulcata, 



Lam. 



Lucina serrala, Dixon. 

 Magnified. 



Fie. 219. 



Conus deper* 

 ditus. 



LOWER EOCENE FORMATIONS OF ENGLAND. 



London Clay proper (C. 1, Table, p. 208). — This formation underlies 

 the preceding, and consists of tenacious brown and bluish-gray clay, 

 with layers of concretions called septaria, which abound chiefly in the 

 brown clay, and are obtained in sufficient numbers from sea-cliffs near 

 Harwich, and from shoals off the Essex coast, to be used for making Ro- 

 man cement. The principal localities of fossils in the London clay are 

 Highgate Hill, near London, the island of Sheppey, and Bognor in Hamp- 

 shire. Out of 133 fossil shells, Mr. Prestwich found only 20 to be com- 

 mon to the calcaire grossier (from which 600 species have been obtained), 

 while 33 are common to the " Lits Coquilliers" (p. 228), in which only 

 200 species are known in France. We may presume, therefore, that the 

 London clay proper is older than the calcaire grossier. This may perhaps 

 remove a difficulty which M. Adolphe Brongniart has experienced when 

 comparing the Eocene Flora of the neighborhoods of London and Paris. 

 The fossh species of the island of Sheppey, he observes, indicate a much 

 more tropical climate than the Eocene Flora of France. Now the latter 

 has been derived principally from the gypseous series, and resembles the 

 vegetation of the borders of the Mediterranean Fig. 220. 



rather than that of an equatorial region ; whereas 

 the older flora of Sheppey belongs to an antece- 

 dent epoch, separated from the period of the Paris 

 gypsum by all the calcaire grossier and Bagshot 

 series — in short, by the whole nummulitic forma- 

 tion properly so called. 



Mr. Bowerbank, in a valuable publication on 

 the fossil fruits and seeds of the island of Sheppey, 

 near London, has described no less than thirteen 

 fruits of palms of the recent type J\ r ipa, now only 

 found in the Molucca and Philippine islands and 

 in Bengal (see fig. 220). In the delta of the Ganges, Dr. Hooker ob- 

 served the large nuts of Nipa fruticans floating in such numbers in the 

 various arms of that great river, as to obstruct the paddle-wheels of 



ffipadiUs eMipticw, Bow. 



Fossil palm of Sheppey. 



