188 TRANSACTIONS OF SECTION C. 



Isle of Wight with the Purbeck Hills protected the Tertiaries of the Bournemouth 

 area, forming as they do the boundaries of the Hampshire Basin. But for this 

 fact that the Bournemouth, Bcagshot and Bracklesham beds lie in the syncline 

 of the Hampshire Basin, this area would have been stripped bare to the chalk, 

 as have other unprotected parts of the south coast. The characteristic beauty 

 and scenery of Bournemouth has thus happily been preserved for us, with the 

 pines, gorse and heather which floiu-ish on such soil. In conclusion, mention 

 should be made of several local peculiarities of the Tertiary beds. First, that 

 they all rapidly thin out westward. Secondly, the pipe-clay deposits of the 

 Lower Bagshots" derived from decomposition of granite to the west and brought 

 down by the Solent River. Thirdly, the complete absence of lime, and conse- 

 quently of molluscan remains, from the Woolwich and Reading beds to the 

 base of the Bartons. This is due to prolonged percolation of surface water 

 through the sand. No traces of the prolific shell-life of Selsey are found in the 

 Bracklesham beds of this district. 



2. The Liiholoqical Su£cessi>on in the Avonian of the Avon Section, 

 Clifton. B-ij S. H. Reynolds, Sc.B., F.G.S. 



Several previous workers have dealt with the lithology of the Avon section, 

 and. in particular, Mr. E'. B. Wethered and the late Dr. A. Vaughan. The 

 results of the present paper are based in part on field work, in part on the 

 study of over 200 rock slices which have been cut with the aid of grants from 

 the University of Bristol Colston Society. 



The chief rock-types occurring are the following, the horizons being alluded 

 to under the designation adopted in Vaughan's original paper.' 



Calcareous Bochs. 



Algal limestones are abundant (a) in Km, (Ij) at the top of C2, (c) in 

 the lower part of .Si, (d) in the pisolitic beds of the lower part of S2, (e) in 

 the ' Concretionary Beds ' of the upper part of S, : this is the most important 

 development. 



AlitcJieldeania and Solenopora are the most persistent forms ranging from 

 the base of K to the top of S2. Siiongiostroma is the prevalent form in the 

 calcite-mudstones which are so abundant in C2 and S. 



FoRAMiNiFERAL LIMESTONES : Foraminifera first begin to be fairly common 

 in Z2. They occur in great abundance in the upper part of S2 and the 

 lower part of Di. 



Coral Limestones : Zaphrentid corals play an appreciable part as limestone 

 builders in Zj, whiie bands full of Lithostrotion innrtini are most characteristic' 

 of S. Corals attain their greatest importance in D. 



Crinoidal Limestones : Crinoids are abundant in Ki and K2, and are the 

 greatest limestone builders throughout the whole of the Z beds. 



Br-achiopod Limestones are met with throughout nearly the whole section. 

 Spirifcr, Orthotetes and Chonrfcs being the most abundant Tournaisian genera, 

 Scminula, Prodnctiis and Chonetes the commonest Visean. 



Ostracods are very plentiful wherever the rocks are shaly or of the calcite- 

 mudstone type, viz. : throughout K. at the top of Ca. and in the lower part 

 of Si. 



Oolites occur at the following levels : [n] in the upper part of Ci, (h) in 

 the middle of S2, (c) throughout D. 



Siliceous Rocks. 



Crrits are met with only in the D beds. Chert bands occur (a) near the 

 middle of Z,, {h) in S„ below the oolite, (c) in S, between the oolite and the 

 ' Concretionary Beds.' 



' Q.J.G.S., vol. l>;i. (1905). 



