J. P. BLAKE ON THE KIMMERIDGE CLAY OE ENGLAND. 205 



Echinoderms. Only the discovery of such a fauna would justify 

 the recognition of Middle Kimmeridge beds. 



All the rest, then, I include under the title Lower Kimmeridge, 

 with the exception of a few beds forming the passage from the 

 Coral E-ag. Undoubtedly we might call the latter Lower Kimme- 

 ridge and all the rest Middle, as it would appear that Oppel would 

 have done; but there are objections to this. In the first place, the 

 thickness of these passage-beds is quite inconsiderable compared 

 with the others ; they are also only developed, as it would appear, 

 where the Coral Rag is present, and contain in a large proportion a 

 Coralline fauna ; but, chiefly, the fossils of the clays above them do, 

 and their fossils do not, bear comparison with those of the zone of 

 Astarte supracorallina, as will be seen in the sequel. 



The series may be best studied inland, particularly in Lincoln- 

 shire, which agrees with Dorsetshire in this as in the upper part. 



The Horncastle pits, cited by Mr. Judd as belonging to the 

 Middle Kimmeridge, are three in number. They expose some thick- 

 ness (30 feet) of clay, with a few septarian stones, which, how- 

 ever, are not very fossiliferous. They probably belong to the upper- 

 most region, as I could not find in them any examples of Amm. 

 serratus. They contain, however, fossils associated with that Am- 

 monite elsewhere ; and its absence only marks a region in the series. 

 The fossils here obtained are : — 



Ammonites mutabilis, Sow. 

 Rostellaria mosensis, Bicv. 

 Dentalium Quenstedti, Bla. 

 Cerithium crebrum, Bla. 

 Cardium striatulum, Sow. 

 Lingula ovalis, Sow. 

 Avicula asdilignensis, Bla. 

 Pecten Grenieri, Cont. 

 Astarte supracorallina, J)' Orb. 



Nucula Menkii, Bom. 

 Nucula, sp. 



Corbula Deskayesia, Buv. 

 Area reticulata, Bla. 

 Anatina minuta, Bla. 

 Homomya compressa, Ag. 

 Thracia depressa, Sow. 

 Serpula intestinalis, Ph. 



We see at once that this is a fauna quite distinct from that of the 

 upper beds at Eulletby, two miles to the N.E., and that we have 

 reached a region as distinct palseontologically as it is lithologically. 

 As these pits, from their stratigraphical position, as well as their 

 contained fossils, are certainly as high in the Lower Kimmeridge as 

 any seen in Lincolnshire, it is important that we should examine this 

 list, incomplete as it no doubt is, to see if it affords any justification 

 for a separation between the beds here and the lower ones at Market 

 Easen and elsewhere. Now, of the seventeen here quoted, every one 

 is found in company with Amm. serratus in other pits in Lincoln- 

 shire; and I fully believe a longer search would reveal that Ammonite 

 here. Three also, namely Avicula asdilignensis, Thracia depressa, 

 and Serpula intestinalis, go down to the very lowest beds. This set 

 of pits, therefore, cannot be separated from the rest ; are they all, 

 then, to be called Lower, or Middle Kimmeridge ? 



Bearing in mind the different horizons of species, as before men- 

 tioned, in different localities, which will account for the presence of 

 JRostellaria mosensis, although it is not a very common fossil here, 



