and its Organic Remains, 91 



folk it is not unusual to find the Terebratula plicatilis and other 

 fossils of the chalk associated with those of the crag; now our 

 extensive acquaintance with organic remains enables us to 

 ascertain that these have been derived from a secondary for- 

 mation. If, then, the action of the waters which deposited the 

 red crag was sufficient to break up the chalk, and mingle its 

 shells with species then living, what would be the natural re- 

 sult of the same force exerted upon the sandy beds of the 

 coralline crag, abounding with Testacea, and offering com- 

 paratively no resistance to the abrading influence of tides and 

 currents? We can hardly imagine any limitation of the extent 

 to which the organic remains in the one would not become 

 blended and interspersed with those in the other. The very 

 recent appearance presented by many of the Turbines and 

 Buccina, found only in the upper beds, when compared with 

 species common to both, is certainly in favour of this view of 

 the subject. I would, however, bring it forward rather as a 

 suggestion than as considering it necessary to advance such a 

 theory in support of the opinions which I have advocated re- 

 specting the separation of the tertiary beds in Suffolk*. 



Should the facts which have now been adduced furnish 

 sufficient data for arriving at that conclusion which it was my 

 principal object to establish, we shall in the next place be led 



* If the German Ocean were now to overflow the eastern counties of 

 England, no one for a moment would think of asserting that a deposit left 

 by it would be contemporaneous with the crag ; and yet the connexion as 

 shown by the shells would be just as great as in the instance before us. 

 Of 111 species from the red crag, M. Deshayes identifies 44 with those 

 now inhabiting the neighbouring seas. Of 370 species found in the coral- 

 line, Mr. Wood identifies 150 with those in the overlying deposit. The 

 proportion in both instances would be very nearly the same, about 40 per 

 cent. We can, therefore, entirely reject the idea of one deposit having 

 derived some of its shells from the other, and yet a wide interval may have 

 elapsed between the formation of the two. 



There will, however, be no reason for adopting one theory to the entire 

 exclusion of the other. Both may be taken into consideration, as account- 

 ing for the presence of the same species in different deposits. We see a 

 similar occurrence, though not to so great an extent, in the subdivisions of 

 the oolitic series. 



Many parts of the red crag were extremely favourable for the preserva- 

 tion of shells, as is shown by the perfect condition of the CardiumParkinsoni 

 and Mytilus antiquorum, both particularly fragile species ; and yet the whole 

 line of coast from Walton-on-the-Naze in Essex, to Orford in Suffolk, with 

 the numerous inland quarries, have furnished only 235 species, while the 

 370 from the coralline were procured by Mr. Wood exclusively from two 

 spots in the neighbourhood of Ramsholt. This great difference in the 

 amount of species would appear quite anomalous if we regard them as 

 belonging to the same period; but the consideration that those in the co- 

 ralline crag were deposited by an ocean inhabited by a larger number of 

 Tettacea, at once accounts for the circumstance. 



N2 



