i 74 Passage of Species. 



Wotton-under-Edge, in Gloucestershire, the Upper 

 Lias clay is very poorly developed, and between 

 it and the ordinary limestone of the Inferior Oolite, 

 there are thick beds of soft brown sand, with inter- 

 mittent hard, sandy, calcareous bands, containing 

 Ammonites, Belemnites, Pentacrinites,and bivalve shells. 

 Above these there are bands of impure sandy limestone, 

 called in 1856, by Dr. Wright of Cheltenham, the 

 Cephalopoda bed, because of the prevalence in it of 

 Ammonites, Belemnites, and Nautili, some of which, 

 with other forms, are also common in the Upper Lias 

 clay. This fact induced him to consider these sands 

 and impure limestone to be so intimately related to 

 the Upper Lias, that he named them in his Memoir 

 6 the Upper Lias Sands ' l instead of ' the Mitford Sands 

 (of the Inferior Oolite,') a name long before given to 

 them by William Smith. 



According to existing lists, 17 species of Conchifera 

 pass from the sands into the overlying Oolite strata, 

 and, indeed, about 39 or 40 species of all kinds are 

 common to the Upper Lias and the overlying Oolitic 

 formations, 2 thus linking the Lias to the Oolites in a 

 continuous chain of specific life. 



Throughout the southern half of England, from the 

 English Channel to the borders of Northamptonshire, 

 the various members of the Oolitic series maintain a 

 tolerably uniform character. 



THE INFERIOR OOLITE LIMESTONE forms the lowest 

 member of this series. It first appears between the west 

 end of the Chesil Bank and Bridport Harbour in Dorset- 

 shire, from whence, underlaid by the before-mentioned 

 sands, broken and interrupted by many faults, it ranges 



1 * Journal of the Geol. Soc.' 1856, p. 292. 



2 As catalogued by Mr. Etheridge. 



