TRANSACTIONS OF SECTION C. 513 



Oligocene without anj' perceptible change or break; but few, or none, of the same 

 species pass down or occur with the Alum Bay beds. 



These Middle Bagshots are represented in Alum Bay by the unfossiliferous 

 beds marked 10 to 24 in Professor Prestwich's section,^ and are 240 feet thick. 

 Palseontologically, these beds may be correlated with the continental Eocenes, pro- 

 bably those of Aix-la-Chapelle. The cliffs fronting the sea may be divided into 

 three groups. The first extends from Poole Harbour to Bateman's Chine, the 

 second group extends from the Sugar-loaf Chine to Watering Chine, the third 

 section or group extends from AVatering Chine to the Bourne Valley.^ The chief 

 interest attached to the Bournemouth beds is the flora distributed chiefly through 

 the ' Lower or FresMcater Series.' None of the prevailing Alum Bay types are found 

 at Bournemouth, nor are any of the well-known Bournemouth types found at Alum 

 Bay, and according to Mr. Gardner, their affinities are completely with the floras 

 ascribed in France to the Oligocene, and the forms of flora as at present known, 

 chiefly Australian and tropical American. 



The author has endeavoured to show that ' a great river existed throughout the 

 whole of Eocene times, bringing deposits from the westward, and that the Bourne- 

 mouth cliffs present a section across its bed, these deposits being formed during a 

 continued period of subsidence.' ' The sudden change observed in the beds from 

 fine to coarse sediment, and the thickness of the deposit, cannot be explained by the 

 floods and freshets incidental to changing seasons, but are such as would occur 

 whenever subsidence exceeded, in however trifling a degree, the silting up power 

 of the river,' loc. cit. p. 13. 



It is a question of importance whether the continental floras similar to our own 

 at Bournemouth have been correctly determined. ' For while all the strata that 

 have yielded dicotyledonous leaves or fruits below our Headon series are admitted 

 to be Eocene, scarcely any of the beds on the Continent resembling them are 

 ascribed to that age,' but to the Miocene. ' For as all Eocene floras approximate 

 more or less to Miocene, it has been a kind of rule in the absence of stratigraphical 

 evidence, to assume that all isolated patches with dicotyledons, belonged to the 

 latter period,' and had the stratigraphical evidence at Bournemouth been incon- 

 clusive, the whole of that Eocene formation must also upon plant evidence (for we 

 have no other) have been classed as Miocene. 



The Ldwer Freshiuater series is seen in the neighbourhood of Corfe and some 

 parts of the cliffs at Studland. It is characterised by abimdance of pipe-clays, and 

 IS about 200 feet thick. 



The Middle Freshwater sei-ies also occurs at Corfe and Studland, and forms 

 the whole thickness of the cliffs between Poole Harbour and Bournemouth, thus 

 constituting a fine section, 4 miles long and 100 feet in height. 



The next series is marine, and about 400 to 500 feet thick. This marine group 

 occupies the cliffs between Boscombe and High Cliff". 



The Bournemouth flora appears to consist principally of trees or hardwood shrubs, 

 few remains of herbaceous plants being preserved. The ferns are rare in the lower 

 part of the series, but become more abundant, almost to the exclusion of other 

 vegetation, towards the close of the middle period. 



The prevailing group appears to be that of Acrostichum, of which there were 

 many species. Aru/iopteris, Nephrodium, Gleichenia, and Lyffodium, and other 

 undescribed forms occur. 



Among the Coniferte, Cupressus, Taxodium, and Dacridium, with indications of 

 pinus. The Cycadse seem to have disappeared. 



The monocotyledons are well represented by reeds and rushes. Nipadites 

 represents the screw pines. The palms are very abundant, especially in the lower- 

 most beds of Corfe and Studland and the upper middle beds of Bournemouth; 

 many Flahellaria, Sabal, and Phtenicites occur; the Smilacese occur in all the 

 foasiliferous beds, and are represented by five or six species. 



' Quartirhj Journal of the Geological Society, vol. x. p. 56. 



- For particulars of these three groups, see Quarterly Journal of the Geological 

 Society, xxxviii. pp. 5-8. 



1882. L I 



