475 



PROCEEDINGS 



THE GEOLOGICAL SOCIETY. 



POSTPONED PAPER. 



On the Insect Beds of the Purbeck Formation in Wiltshire 

 and Dorsetshire, By the Rev. P. B. Brodie, M.A., F.G.S. 



[Read June 15, 1853*.] 



Prof. E. Forbes, in a valuable paperf in Jameson's Edinburgh 

 Journal, was the first to divide the Purbeck Series in Dorsetshire 

 into upper, middle, and lower, and to define the varied conditions 

 under which the whole was accumulated. In this memoir he pointed 

 out that this Series consisted of alternations of freshwater, marine, 

 and brackish water deposits, differing as much in their lithological 

 as in their zoological characters, giving us also a new and more 

 enlarged view of the distribution of freshwater and marine life during 

 this portion of the Oolitic period. 



At the time when I first (now nearly thirteen years ago) laid before 

 this Society an account of the occurrence of Insects and other new 

 fossils in the Purbecks in the Vale of Wardour, I was induced to 

 consider the Insect and Isopod limestones as belonging to the lower 

 part of the lower Purbecks. Since then, however, the subdivisions 

 of Professor Forbes, and the joint investigations of my friends the 

 Rev. Messrs. Austen and Fisher, have led me to examine the few 

 available sections in the Vale of Wardour again, and to pay a visit 

 to Durlstone Bay, in order to institute a more careful comparison 

 between these two distant portions of the formation, — the result of 

 which I now proceed briefly to describe. 



Vale of Wardour. 



The upper Purbecks are entirely wanting in the Vale of Wardour|, 

 but the middle and lower are tolerably well developed ; although these 



* For the other Communications read at this Evening Meeting, see Quart. 

 Journ. Geol. Soc. vol. ix. p. 317 et seq. 



t Read at the Meeting of the British Association at Edinburgh, 1850. 



i For a general Section of the Vale of Wardour, see ' History of the Fossil 

 Insects in the Secondary Rocks of England,' pi. 11, and page 1 et seq. See also 

 Trans. Geol. Soc. 2 ser. vol. iv. pt. 2. pi. 7 & pi. 10 a. 



