210 J. F. BLAKE ON THE KIMMERIDGE CLAY OF ENGLAND. 



fossiliferous. Some of the large doggers are almost entirely com- 

 posed of Serpula tetragona ; others contain Avicula cedelignensis ; 

 while the clays are full of Ostrea deltoidea and Belemnites nitidus. 

 There are beside : — 



Ammonites serratus, Sow. 

 Bissoa mosensis, Buv. 

 Cyprina cyreniforms, Bla. 



Lima sedilignensis, Bla. 



Area, sp, 



Tkracia depressa, Sow. 



It was from this pit probably that Sowerby's original specimens 

 of Serpula tetragona came, as he mentions their filling whole blocks 

 and being associated with Avicula inoequivalvis (cedilignensis) and 

 Astarte (probably supracorallina), which latter species we ought 

 therefore to add here to the list. 



It is a remarkable illustration of the persistency of these regions 

 over considerable areas, that in South Yorkshire the Kimmeridge 

 Clay seen has an exactly similar appearance to that at "Woodhall Spa 

 and Hawkstead Hall, and contains Aram, serratus of the Sowerbian 

 form and Ostrea deltoidea at Elloughton ; and near Leavening are also 

 blocks filled with Serpula tetragona and numerous Bel. nitidus and 

 Ostrea deltoidea, associated, however, with Amm. cordatus. Yet 

 this is not the lowest region of the Kimmeridge Clay in Lincoln- 

 shire ; for at Worlaby are met with sandy clays with very few 

 fossils, the fauna being reduced to Lingula ovalis (abundant), Lucina, 

 sp., and Amm. hiplex. From their stratigraphical position they must 

 lie below the last described, and are probably not far above the base 

 of the formation. The exposure here is a very satisfactory one, 

 from its proving, by the presence of Lingula ovalis, that it is still in 

 Kimmeridge Clay ; and therefore, of course, the beds above must be. 

 This series of pits, again, make another well-marked subzone, cha- 

 racterized, as Mr. Judd noticed, by the abundance of Ostrea dilatata 

 and Belemnites nitidus. No WiyncJionella ineonstans, however, is 

 reached ; indeed I have never yet found it associated with Ammo- 

 nites serratus. 



It is well known that the Coral Rag is absent from Lincolnshire, 

 and the succeeding beds are those of Oxford Clay, which may be 

 well seen with their characteristic fossils at Bardney and Lang- 

 worthy. The different exposures of Lower Kimmeridge in Lincoln- 

 shire may be thus arranged in descending order : — 



Homcastle, Hamilton Hill, Brigg, Wrawby (East). 



Market Easen, Wrawby (Middle), Holton Moor. 



Caistor Road. 



Baumber. 



Langton. 

 West Wrawby, West Brankwith, Hawkstead Hall. 



Woodhall Spa. 



Worlaby. 



It is very difficult to estimate the total thickness represented by 

 these various horizons ; but as many of the pits themselves reach a 

 depth of 30 ft., and there are eight stages, it cannot be less than 

 240 ft., supposing that every portion happened to be dug into at one 

 place or another. A more probable estimate would be obtained by 



