part 4] jUEAssic chroj^ologt. 431 



prior to the deposition of strata of the Garaiitiana hemera, much 

 of what may have escaped that destruction perished in later 

 erosions along with the whole of the Inferior Oolite. I have made 

 a rough calculation that possibl}^ not 1 part in 30,000 of the bed 

 as originally deposited has been preserved. I do not pledge mj^self 

 to the figures ; they may be thought to be an under-estimate, but 

 there is also reason to think that they may be an over-estimate. 

 But to give an idea of what such destruction means : there are 

 about 30,000 post-offices in the British Isles enumerated in the 

 Postal Guide. If we were to destroy all these names but that 

 of Sherborne (Dorset), we should thereby obtain a picture of the 

 destruction of the niortense bed. Then consider how small a part 

 a quarr}?- or two forms of the preserved portion, and that, when 

 such quarries are in work, many years may pass without anyone 

 visiting them. On such a basis, it is easy to understand that the 

 collected material may form no more than one part in a million 

 of the entombed originals. 



Which deposit of the Jurassic hemerse has suffered the most in 

 regard to destruction may be a matter for future research, but the 

 Qiiortense bed will, I expect, be one of those which make the 

 greatest claim to such distinction. It is not proposed to enter 

 into details on this subject here — the accumulation of evidence is 

 no light task ; but it is hoped to initiate in a sequel to this paper 

 a geographical enquiry as to the original extent of the niortense 

 bed and as to its present preservation, which may fit in suitably 

 wdth some other geographical studies suggested by stratal and 

 faunal ^^henomena of the rocks to be dealt with in that sequel. 



V. Ceetain Cheo^ological Studies. 



(A) Milborne Wick and the Green-grained Marl. 



In the Table ^ of his paper on the Doulting-Milborne-Port 

 district, Mr. Linsdall Richardson places opposite hiagdeni hemera, 

 and under Milborne Wick, the following ' Marl with green grains, 

 S. S. Buckman.' The placing of it within inverted commas makes 

 it appear like a statement taken from my paper,^ or given on my 

 authority. But this is incorrect : reference to my section of 

 Milborne Wick will show that I divided the beds in more detail 

 than did Mr. Richardson. I recorded 



Himiphriesiani. 2. Soft white chalky limestone, 4 inches. 

 [hiagdeni^. 



3. Grey limestone with iron grains, 6 inches. 

 ■sauzei. 4. White limestone, 6 inches. 



5. [Soft limestone] speckled with green grains. Astarte 

 spissa. 



Here I have said nothing about any green grains in the limestone 

 of hiagdeni hemera : at the top that is white, without coloured 



1 IX, 3, facing p. 518. 2 j^ 3^ p_ 502. 



