OF THE ORGANIC FOSSILS. 421 



are limited in number, and are again marine. The 

 red marl sandstone, like the inferior one, contains 

 very few: and there may be special reasons for this, 

 since there, are peculiarities respecting this stratum, 

 which I shall speak of hereafter. I have already 

 noticed the intermixture of terrestrial and marine 

 remains in the lias series; and if it is at present one 

 of the supposed geological difficulties, this will be a 

 subject for after inquiry. That series has been more 

 boldly described than well understood; as it has 

 been confidently transferred to other countries, 

 under the favourite hypothesis of universal for- 

 mations. It is scarcely necessary to proceed further 

 in the same detail. Organic fossils ought to occur 

 abundantly in the equally abused and hypothetical 

 Oolithe, and they do so: as they do, much less abun- 

 dantly, in the no less hypothetical Green sand, be- 

 coming, finally, abundant in the Chalk. 



I have only to remark lastly, of all these strata, that 

 these fossils are occasionally absent in some places 

 while abundant in others ; but that all these differences 

 can be explained through simple considerations, which, 

 after all that I have already said, it would be super- 

 fluous to suggest. 



So recently as I have described the tertiary forma- 

 tions, I need not repeat what concerns them in 

 this respect. The alluvial soils contain the chief 

 remains of the larger and more perfect ter- 

 restrial animals, yet very partially situated ; and I need 

 not here distinguish among the qualities or origins of 

 these, nor at present notice such remains of mixed 

 origin as they may include. With the loose alluvial 

 matters may also be comprised what I have here 

 termed alluvial rocks, however existing. And those 

 which have been formed in fissures or cavities, or in 



