72 



BRITISH EOCENE ELORA. 



Studland. It maintained its ground during the physical changes of the Middle and 

 Upper Eocene and Lower Oligocene ages, and only migrated away during the lower 

 temperature that accompanied the deposition of the Hempstead beds. Its absence from 

 Alum Bay and the older Bournemouth beds shows that these stations were unsuited to 

 it, probably through want of moisture, while it was excluded from the otherwise suitable 

 swamps of Bovey^ through the higher elevation of that district during the Eocene, and 

 from the swamps of Hempstead, where a palmetto still grew, by decrease in temperature. 

 The localities from which it is absent, no less than those in which it is present, show 

 that this part of England must have been almost on the confines of its range, and the 

 minimum temperature of our Middle Eocene and Lower Oligocene may be gauged to 

 some extent from it. 



The second Eern is so completely identical with the existing Osmunda javanica, that 

 it seems merely misleading to continue to use a separate specific name for the fossil 

 pinnae. Notwithstanding its abundance in both a recent and fossil state, its identity 

 remained unrecognised for twelve years by Heer, who speaks of it in 1869 as Hemite- 

 lites, closely allied to //. Torelli, of Greenland. There is little to add to our former 

 description, though its late arrival and speedy migration from England are both 

 remarkable. Its present range from Kamschatka to Java shows that it might have 

 withstood, better perhaps than most tropical species, a change of temperature, and, 

 indeed, the relatively small size of the pinnae at Bovey, prove that it supported there a 

 lower temperature than in the swampy tracts at Bournemouth, where the pinnae reach 

 nearly twice the size. Its occurrence from the oldest to the newest beds at Bourne- 

 mouth, shows that it existed throughout our Middle Eocene and was not specially 

 localised, so that its absence at Hord well. Gurnet Bay, and Hempstead, where many of the 

 associated plants of Bournemouth and Bovey survived, seems a reality. Like the 

 Chrysodimii it must, with its Cycas-like growth, have formed a conspicuous feature in 

 the swamp vegetation of Bournemouth. Though apparently strictly a Middle Eocene 

 Eern with us, Saporta states that it is confined to the Oligocene in the South of France, 

 a dryer atmosphere and soil doubtless excluding it from the Eocene of Aix in Provence, 

 while farther east, the strata in which it is found seem even newer. From this visible 

 migration eastward it might almost be inferred that it reached its present habitat, the 

 extreme east of Asia, and the islands to the south, from the westward, and incidentally 

 that it failed to penetrate into Hindustan^ on its route on account of some impassible 

 barrier. It seems likely that this Fern may be useful in fixing the age of plant remains 

 in England, and perhaps also in the South of France, though it must not be inferred 

 from its presence that deposits in different countries are contemporaneous, since, as 

 a still existing species, it might occur in any tertiary or quarternary deposit where 



1 Bovey-Tracey is eighty miles distant from Bournemouth, and situated among hills, whence some of 

 the Eocene river sediment was probably derived. 



2 It is only met with in southern India. 



