De Ranee — On the Albian or Gault of Folkestone. 163 



clay. This trituration, with its step-like results, is quite distinguish- 

 able in its effects from the phenomena of the slopes extending 

 upwards on either side of the actual present and past channel. The 

 limestone forms, as usual, a terrace in the side of the fells, and shews 

 picturesque cliffs. Below this we get pale flaggy beds with shale, 

 the former exhibiting fine markings of two species of Crossopodia. 

 Through these the burn descends past the village of Middleton 

 down to its junction with the river, in the four fathom limestone. 



I closed a pleasant day's ramble in the conviction that we had not 

 made much progress in the valley question since the days of Hutton, 

 simply because a physical fact once ascertained becomes an axiom. 

 What more can be said than the following : — " The original in- 

 equalities of the surface, and the disposition of the strata, must, no 

 doubt, have determined the water-course at first ; but this does not 

 hinder us from considering the rivers as having modified and changed 

 those inequalities, and as the proximate causes of the shape and 

 configuration which the surface has now assumed." — Flay fair, Illus- 

 trations of the ffnttonian Theory, p. 357. 



IV. — On the Albian, or Gault, of Folkestone. 

 By C. E. De Eance, of the Geological Survey of England and "Wales. 



FROM the proposition of Professor Forbes, that a species once 

 extinct never reappears, it follows that when a species recurs, 

 it must have existed elsewhere during the whole of the time occupied 

 by the deposition of the strata between the deposits containing it. 

 In viewing the distribution of species through the chief stages of the 

 Lower Cretaceous system, it appears that the same species reappear 

 when there is a recurrence of the same or similar physical conditions, — 

 the Neocomian and Albian clays having more species in common than 

 the intervening Aptian ; and the Aptian and Cenomanian sands, being- 

 more closely allied than the intervening Albian clay. An examination 

 of the latter, at Folkestone, appears to allow of its being divided into 

 eleven lithological stages or beds which have been more or less re- 

 cognized by all geologists and fossil collectors who have visited 

 the district. To these beds provisional names have been assigned 

 expressive either of their colour, position, or characteristic fossils. 

 But in tracing all the recurring species from their genesis in one 

 stratum to their extinction in another, these beds are found to have 

 no great palseontological value, but to resolve themselves into two 

 groups divided by a junction bed, in the same way as the *' junction 

 bed" separates the Albian from the Upper Aptian. Beds i, to iii. 

 forming an Upper, beds v. to x. a Lower Albian, beds iv. and xi. 

 being the two phosphate junction beds. 



As Mr. Judd,^ in his admirable paper on the " Speeton Clay," has 

 adopted D'Orbigny's term, "Neocomian," for that formation, the 



1 Geol. Mag. Vol. V. p. 141. 



