Wood— Structure of the Thames Valley.. 99 



the succession of life^on th.e land and in the waters, will welcome 

 every additional fact which may tend to clear up the history of that 

 remarkable deposit. A lagoon with bordering marshes, and dryer 

 land ; the water full of marine life — Corals, Mollusca, Crustacea, 

 Fishes, Turtles, and Teleosaurs ; — the land occupied by Cycadaceous 

 and Coniferous plants, and traversed by the huge Megalosaur and 

 the tiny Phascolotherium ; while over land and water the Pterodac- 

 tylian Harpies stretched their ^Iraj wings. 



Semel insanivimus omnes ! Most of us have been fly-catchers in 

 our day. I was myself a zealous student of insects ; and remember 

 nothing with more pleasure than the chase of Agrion, AesJina, or 

 Libellula, by the side of some Yorkshire water. No doubt such 

 waters were haunted "in the Oolitic days" by the insects we are 

 now considering, and it becomes an enquiry" of some interest in the 

 further study of them, whether they manifest any special affinity 

 with congeneric forms now visible in Australia, as do the Cycads, 

 WaldJieimia, Trigonia, Cucull<^a, and PJiascolotheria, which are their 

 companions in the deposits of Stonesfield, with the plants, shells 

 and mammals of that old-fashioned corner of the earth. 



EXPLANATION OF PLATE VI. 



Figs, a and b. Impression and counterpart of the wing of Libellula Westwoodii, 



Phillips. Natural size. From the Stonesfield Slate. 

 h. s marks the position of the "stigma." 

 e. Enlarged view of central portion of wing, 

 d. Enlarged view of Aeshna Broddmi, Morris. From the Lias of Dumbleton • 



(Placed for comparison with Libellula Westwoodii.) Figured in " Brodie's 



Fossil Insects," Tab. 8, fig. 1. 



II.- — On the Steuoture of the Thames Valley and of its 



Contained Deposits.^ 



By Searles V. "Wood, jun., F.G.S. 



WHILE we have in the deposits described no sig-ns Of any line of 

 drainage conterminous with the valley through which the 

 Thames now finds its way from London to the sea, until after a 

 series of diverse conditions, and until a most recent date, — that of 

 the Marsh clay, we shall find, in the physical structure of the 

 valley, evidence corroborative of that afi'orded by the deposits ; and 

 showing that the present valley of the Thames is a creation subsequent 

 to all the deposits which it contains that are older than the Marsh clay.' 

 So far from the Thames gravel extending " in a continuous and 

 uninterrupted sheet from the sea to Maidenhead," it stops entirely 



' Concluded from our last number (p. 63). 



2 It has been contended that the Thames was once a tributary of the Rhine, but this 

 argument can only have been supported by those who have not studied the structure 

 of the valley, and of the East of England, with the minuteness that would show such 

 a viewto be at variance equally with the mode in which the valley was first formed, 

 and with the conditions which it subsequently underwent, i.e., with its excavation 

 through the Drift by denudation on emergence from the Upper Drift sea, and its 

 subsequent history as given here in outUne. 



