220 



LOWER EOCENE STRATA OF ENGLAND. [Ch. XVI 



oceasioDally represented in one area by land, in another by an estuary, in 

 a third by the sea, and even where the conditions were in both areas of a 

 marine character, there was often shallow water in one, and deep sea in 

 another, producing a want of agreement in the state of animal life, 

 • But in regard to that division of the Eocene series which w^e have now 

 under consideration, we find an exception to the general rule, for, whether 

 we study it in the basins of London, Hampshire, or Paris, we recognize 

 everywhere the same mineral character. This uniformity of aspect must 

 be seen in order to be fully appreciated, since the beds consist simply ol 

 sand, mottled clays, and well-rolled flint pebbles, derived from the chalk, 

 and varying in size from that of a pea to an egg. These strata may be 

 seen in the Isle of Wight in contact with the chalk, or in the London 

 basin, at Reading, Blackheath, and AVoolwich. In some of the lowest of 

 them, banks of oysters are observed, consisting of Ostrea bellovacina, so 

 common in France in the same relative position, and Osirea edulina, 

 scarcely distinguishable from the living eatable species. In the same 

 beds at Bromley, Dr. Buckland found one large pebble to which five 

 full-grown oysters were affixed, in such a manner as to show that they 

 had commenced their first growth upon it, and remained attached to it 

 through life. 



In several places, as at Woolwich on the Thames, at New Haven in 

 Sussex, and elsewhere, a mixture of marine and freshwater testacea dis- 

 tinguishes this member of the series. Among the latter, Milania inqui- 

 nata (see fig. 234) and Cijrena cuneiformia (see fig. 233) are very com- 



Fis. 233, 



Fig. 234. 



Cyrena cuneiformis, Miii. Con. 

 Natural size. 



3/elania inquinata, Des. Nat. size. 

 Syn. Cerithium inelanoides, Min. Con. 



mon, as in beds of corresponding age in France. They clearly indicate 

 points where rivers entered the Eocene sea. Usually there is a mixture 

 of brackish, freshwater, and marine shells, and sometimes, as at Woolwich, 



