J. S. Gardner — Revision of the British Eocenes. 471 



Hordwell show that tropical conditions had not diminished on 

 land, though the marine fauna had become so conspicuously more 

 temperate. The Headon Beds are first fluviatile, then marine or 

 estuarine, but singularly the fauna of Brockenhurst recalls that of 

 Bracklesham almost as much as the more immediately preceding 

 Barton fauna. Fresh fluviatile beds come in and the strata continue 

 to be of freshwater origin, until the Bembridge Marls in the east of 

 the Isle of Wight betray brackish water, and the still newer Hemp- 

 stead Beds in the west even more decided marine conditions. The 

 temperature during the later stages seems gradually to have din)in- 

 ished, for fresh species of the same genera of mollusca continually 

 succeed each other, while the flora, without changing its general 

 character, seems to have lost its more tropical forms. It is unneces- 

 sary to describe the beds, but they are more distinctly freshwater to 

 the west than east. They are crowded throughout with fossils, the 

 assemblage of Pulmonate Gasteropods in the Bembridge Limestone 

 being especially remarkable. In places I have seen this bed crowded 

 with casts of the eggs and young of the gigantic Bulimus, now con- 

 fined to the West Indies, and large species of Achatina and Helix 

 are well-known fossils from it. Between Yarmouth and Gurnet 

 Bay the shore used to be fairly sprinkled with scutes of turtle and 

 crocodile and mammalian teeth, and the floras of Hempstead and 

 Gurnet Bay are celebrated. 



I do not think, if three divisions of the Eocene and an Oligocene 

 formation are to be maintained, that any other arrangement would 

 separate the divisions where natural breaks occur, and yet leave 

 them of approximately the same importance. 



It is obvious, from the extension of similar formations over Northern 

 Europe, and their absence to the South, as well as from their English 

 distribution, that the Lower Eocenes and the London Clay were 

 deposited by a sea whose chief extension lay in northern directions. 

 The Lower Eocene deposition was accompanied by a slight depres- 

 sion in the littoral and delta areas, and was checked by a slight up- 

 heaval. During the consequent retreat of the sea, the great Oldhaven 

 beaches must have been formed and left stranded. The fauna and 

 flora show the climate to have been almost as temperate as at the 

 present day, and hence it must be inferred that the Greenland Lower 

 Eocene rocks, which are barren of plants, were formed during this 

 period. The London Clay deposition was favoured by greater 

 depression, during which the sea penetrated to the utmost limits of 

 Hampshire and into Dorsetshire. In the east the sea must have been 

 over a hundred fathoms deep, but westward it was shallower, and 

 the " clay " is finally represented by shingles and sand. During this 

 period a remarkable change took place in the climate, which became 

 almost tropical, causing the older flora of the temperate Eocene 

 period in England to migrate towards the Pole and establish itself 

 in Greenland. The so-called Miocene flora, of Greenland at least, 

 is a continuation of our Lower Eocene flora, and probably belongs 

 to the Middle Bagshot or most tropical of English Eocenes. 



It is interesting to trace out the presence of a large river flowing 



