212 Mr. De la Beche on the Distribution of Organic Remains. 



therefore conclude that dry land existed in, or not far distant 

 from, the comparatively small space containing the organic re- 

 mains enumerated in the foregoing table ? The principal de- 

 posits of carbonaceous matter would seem to be Brora and 

 Yorkshire. 



Most of the great Saurians now buried in the oolite would 

 seem also to have required the protection of land ; for though 

 the Ichthyosauri might, like the Porpesse, brave the waves of 

 an ocean, the structure of the Plesiosauri would seem to unfit 

 them for such exposure; and, judging from the habits of mo- 

 dern crocodiles, the ancient species are not likely, from choice, 

 to have quitted the neighbourhood of land. The Pterodactyles 

 probably flew over the land, and the Didelphys must have lived 

 upon it. 



The quantity of corals contained in the forest marble, great 

 oolite, or coral rag, would seem to show that the places, where 

 these remains are the most abundant, must have had a compa- 

 ratively shallow covering of water at the time these Zoophytes 

 existed. 



The evidence, therefore, would seem to be in favour of a com- 

 paratively shallow sea, interspersed with dry land, for the for- 

 mation of so much of the rocks usually termed oolitic, as occur 

 within the space treated of in these notes. The great abun- 

 dance of Oysters and Gryphites may probably also be in favour 

 of comparatively shallow water*. 



I have been thus particular in enumerating what may appear 

 to be evidence of comparatively shallow seas, because the same 

 deposit may have been, and probably was, going on in conti- 

 guous and deeper portions of the ocean, and because these con- 

 tinuous portions of the same formation may differ very consi- 

 derably both in mineralogical and organic character. Thus 

 the oolitic series of England and of France may be represented 

 even so near as Italy and Greece, by a series of beds so differ- 

 ent in organic contents, as at first sight to be considered di- 

 stinct. 



Endeavours to trace the small divisions into which the oolitic 

 series of England has been separated, are no doubt useful if our 

 attention be directed to an examination of the areas over which 

 certain minor causes may have operated : but when these small 



* It is remarkable that the three great argillaceous deposits of the oolitic 

 series contain an abundance of either Gryphites or Oysters, and that the 

 Saurian remains are most commonly observed in the same strata. Thus the 

 Ostrea deltoidea in England, and the Gryphaea virgula in France, have 

 been termed characteristic of the Kimmeridge clay; the Grypha?a dilatata 

 is a common shell in the Oxford clay; and the Gryphaea incurva Sow. 

 (G. arcuata Lam.) is abundant in the lias. 



divisions 



