330 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



It thus seems that, with the exception of three extinct species (4, 

 8, and 13) which are local, and two (7 and 11) recent northern species, 

 the remaining eleven have or have had a southern range, — three as 

 far as Central France, and eight as far as the Mediterranean. The 

 other genera also as a group exhibit more southern than northern 

 affinities. 



The connection, before suggested, of an extension of this older 

 Crag eastward and southward over our chalk-downs would account 

 for the introduction of the several more southern forms of Molluscs*. 

 There are even circumstances connected with this inquiry which ren- 

 der it possible that these Lenham beds may be a stage older than 

 the Coralline Crag ; for a considerable number of the fossils, so far 

 as such imperfect specimens will allow us to judge, do not apparently 

 belong to either the Coralline or the Red Crag ; and are either new 

 species or may be found to agree with some of the older Pliocene, or 

 Upper Miocene, species of France. This can only be determined 

 when we are in possession of better and more specimens, or discover 

 some fresh fossiliferous localities. 



I have shown on a former occasion, that the axis of the Weald 

 was probably one of elevation at the commencement of the Creta- 

 ceous period, — further, that at the commencement of the Tertiary 

 period the chalk had been so planed down around the "Weald, that 

 there could be little doubt that in the centre of the then Wealden 

 area, the Upper and Lower Greensands were exposed, and that their 

 debris contributed towards the formation of the Lower London Ter- 

 tiary beds. Now, again, at this early Crag period it would appear 

 that these Lower Tertiaries, together with the London Clay, which 

 had during a period of subsidence partly, if not entirely, covered up 

 the old Wealden island, were also largely denuded, and that the 

 Crag was deposited in depressions between the remaining outliers of 

 the Tertiary strata, resting in places upon the again bared surface 

 of the Chalk. At the same time it is evident, from the lithological 

 structure of these presumed Crag beds, that they must have derived 

 their origin, not only from the debris of the Tertiary strata, but more 

 from that of the Lower Greensand and adjacent strata, for the chief 

 materials of the Lenham and Paddlesworth beds are yellow and 

 ochreous sands more or less mixed with yellow and red clay, quartz- 

 ose grits, small quartz-pebbles, and green sand — all common and 

 prevailing constituent parts of the Lower Cretaceous series of Kent. 

 Added to this, the prevalence of iron, derived probably from the 

 Lower Greensand, and again concreting a portion of the Crag sands de- 

 rived from the same older strata t — and giving therefore to this newer 

 iron-sandstone a like appearance to the older, — and of flints derived 

 from the chalk, leads me to believe that another island existed in the 

 Wealden area at the commencement of the Crag period, and that the 



* Not that that communication was uninterrupted ; it was broken by an old 

 Wealden island. 



f Still from the Tertiary strata in part, as the Crag sands often contain the 

 common Lower Tertiary flint-pebbles, — generally scattered, but sometimes in thin 

 seams, and in masses, — together with certain white flint-pebbles. 



