prestwich — t\oolwich and reading series. 13" 



Note. 



The observations on the age and structure of the Tertiary series, 

 from the Chalk up to the Fluvio-marine strata of Hampshire, which 

 this paper completes, having been brought forward at intervals 

 during a period of seven years, some changes have necessarily sug- 

 gested themselves during the progress of the inquiry. On the main 

 points connected with the Marine Eocene strata, I have nothing 

 material to alter ; but as in my first paper ( Journ. Geol. Soc. 

 vol. ii.) I retained the term "London Clay" to the clays of Barton, 

 from its having been previously so applied, and termed the brown 

 clays with organic remains (Strata 4-6) the " Bognor clays," and 

 which I had occasion afterwards to show were the equivalents of the 

 London Clay proper, I dropped the latter name with regard to the 

 Barton clays, and retained it for those beds only which I had before 

 called the " Bognor clays." This, I believe, has caused some uncer- 

 tainty as to the arrangement which I proposed ; I therefore have 

 annexed a diagram, showing the relations of the London and Hamp- 

 shire Tertiary systems, and the order of superposition of the different 

 formations, according to the terms last employed (PI. I. General 

 section) . 



I had hoped to have been able to resume the examination which I 

 commenced, in the lower part of the Tertiary series of the Isle of Wight, 

 in 1839 ; but want of time and other engagements interfered with 

 that intention. It was therefore with great pleasure that I found the 

 inquiry with regard to the structure and age of the Fluvio-marine 

 series taken up by Prof. E. Forbes. Having necessarily had occasion, 

 in the course of the investigation of the Woolwich beds described in 

 the preceding pages, to inquire into the range and character of the 

 fossils of that group more particularly than in the indirect reference 

 to its fossils made in my Isle of Wight paper, I found that some 

 identities which I had given in proof of several species being common 

 to the "Lower London Tertiaries " and to the Isle of Wight Fluvio- 

 marine series, were wrong. This arose in some measure from errors 

 of observation of my own, and from confounding together species 

 differing in character, but which had the same specific name given 

 to them by different authors ; also from taking the localities of the 

 species from the figures and descriptions in Sowerby's ' Mineral 

 Conchology,' without being aware at the time of several corrections 

 which that author had introduced in a supplementary list published 

 at a later period ; and partly from the range and identities given to 

 some species in M. Deshayes's ' Coquilles Fossiles des Environs de 

 Paris,' respecting which the author appears to have been wrongly 

 informed. As the results at which Prof. Forbes has arrived are of very 

 great interest and importance, I hasten to correct these mistakes, lest 

 any partial argument adverse to his views might perchance be founded 

 upon them. 



In the paper above referred to I gave a list of 78 species of shells 

 from the Fluvio-manne beds of Headon Hill ; and I endeavoured to 



