468 J. 8. Gardner — Revidon of the Briiuh Eocenes. 



with the sea deposits of Heme Bay, even though they were actually 

 traceable as a horizontal formation directly overlying the Heme Bay 

 formation. Beaches are the last sediments that can be left by a 

 receding sea in an area of elevation ; and to consider the Lower 

 Eocene beaches as a distinct formation, except lithologically, can 

 only delay any appreciation of the real conditions under which our 

 Eocene strata were formed. The Oldhaven division, I submit, 

 should only be recognized as one of quality — not time — partially 

 overlying and overlapping the marine beds of the Thanet sands. 



The difference between sea-deposits formed under water and those 

 cast up by tidal action on the sea-margin is usually apparent enough, 

 but the classification of the Lower Eocenes is greatly complicated 

 by the intercalation of deposits, both brackish and purely freshwater, 

 formed in a river estuary. These are the Woolwich and Beading 

 Beds. In the western part of the Hampshire Basin they are chiefly 

 mottled plastic clays, becoming eastward gradually more and more 

 mixed with beds of sand. The mottling process has destroyed every 

 trace of organisms, though their freshwater origin and the derivation 

 of the material is quite apparent. The mottled clay is seen in 

 diminished thickness at Beading, where it is underlain by freshwater 

 clays, which, not having undergone this chemical change, still pre- 

 serve their plant remains, and the freshwater deposits extend to 

 Woolwich. Above them are brackish or salt-water estuarine deposits. 

 While the great mass of the Oldhaven Beds show a retreating sea, 

 these estuarine beds show encroaching salt-water ushering in the 

 London Clay Sea, without any intervening beach, so that it becomes 

 important to separate the period of retreat from the peiiod of advance, 

 as well as to recognize the position of the permanent Lower Eocene 

 estuary, over which no beaches were ever deposited. Such estuarine 

 beds occur principally over the west of Kent, East SuiTey, South 

 Essex, with an important outlier at Newhaven in Sussex. 



The Lower Eocene of England is thus a well-marked division, 

 consisting of fluviatile beds in the west, passing east into estuarine, 

 and finally into marine beds. These conditions may have been and 

 doubtless were contemporaneous to a great extent, but the divisions 

 into which they are classified must rather be held to mean distribu- 

 tion of quality or origin than an absolute sequence in time. It is 

 essential, if the extent of the old Eocene estuary is ever to be mapped 

 and understood, that a separate term should be used for the estuarine 

 beds, and it has been suggested that the existing term " Woolwich 

 Beds" might with advantage be kept for them, whilst "Beading Beds" 

 should distinguish those of purely fluviatile or freshwater orig'in. 



Pal^ontologically scarcely anything is known of the Vertebrata 

 of this Lower Eocene period, and our knowledge of the Fauna is in 

 fact almost limited to its Testacea. Only eight specifically deter- 

 mined marine Gasteropods are given in the Survey list for the whole 

 group. Of these, six range throughout, and four survived in the 

 London Clay. Of thirty-two Conchifera, excepting the genus Nucnla, 

 only three are confined to the Thanet Sands as defined by the Survey, 

 and none are stated to be special to that section of it which has been 



