216 J. F. BLAKE ON THE KIMMERIDGE CLAY OE ENGLAND. 



the number of fossils common to the Oxford and Kimmeridge Clays, 

 taking those of the former from published lists and figures. I have 

 myself found Ostrea dilatata with its associated Serpula intestinalis 

 in both; and Avicula dorsetensis, found in Kimmeridge at Bingstead, 

 occurs in Oxford Clay in Lincolnshire, and Ammonites cordatus in 

 the Kimmeridge of Yorkshire. Thracia depressa is commonly re- 

 corded from both formations ; and several of the vertebrate fossils 

 which I have received as from the Kimmeridge, though not found by 

 me in situ, are figured by Prof. Phillips as from the Oxford Clay, as 

 RhampJwrhynchus BucJclandi, Ischyodus Egertoni, Hybodus grossi- 

 conus. But what has struck me most is the almost exact resem- 

 blance, not to say identity, between the Astarte carinata, Corbula 

 Macneillii, and Area subtetragona, as figured by Prof. Morris * from 

 the Kelloway Hock and Oxford Clay, near Chippenham, with the 

 Astarte supracorallina, Corbula Deshayesia, and Area rliomboidalis, 

 which are so highly characteristic of the Kimmeridge Clay. Prof. 

 Phillips also records Discina latissima from the Oxford Clay ; but 

 this perhaps requires confirmation. If all these, and others of more 

 doubtful authority, are really common to the two formations, we are 

 scarcely justified in separating them as Middle and Upper Oolites. 

 In Lincolnshire they are one continuous formation, scarcely more 

 distinct by their fossils than the two divisions of the Kimmeridge 

 Clay; and they partake together of the thinning- out as they enter 

 Yorkshire. But this subject requires further investigation. 



Conclusions. 



The Kimmeridge Clay in England is divisible into two sections, 

 Upper and Lower, and, when preceded by the Coral Bag, possesses 

 at the base a series of no great thickness, which we may call the 

 Kimmeridge Passage-beds. . 



The Upper Kimmeridge is fairly comparable to the lower portion 

 at least of the Virgulian group of foreign authors. 



It consists of paper-shales, paper-slabs, bituminous shales, and 

 cement-stones, with clays interstratified, and may reach a thickness 

 of 650 feet and more. Its fauna is characterized by a comparative 

 paucity of forms, but an infinity of individuals. All the great 

 Saurian remains from near Kimmeridge belong to this portion of 

 the series. 



It is of considerable thickness in Dorsetshire and Lincolnshire, but 

 is very inconsiderable or absent in the inland counties. 



No distinct fauna comparable to that of the Middle Kimmeridge 

 or Pterocerian group has yet been discovered in England, though 

 several of the less peculiar fossils of that group are found associated 

 with Lower Kimmeridge forms. 



The Lower Kimmeridge is a mass of blue or sandy clay very little 

 stratified, with numerous calcareous doggers. It is largely and typi- 

 cally developed in Lincolnshire, where it shows well-marked regions, 

 which exhibit, however, such a gradual community of fossils, that 

 they cannot be made the basis of subdivision, but must be con- 

 * Quart. Journ; Geol. Soc. vol: vi. p. 317, 1850. 



