230 CATALOGUE OP THE LOCAL EOSSILS IN THE 



interior of the country during the submergence of the land after 

 the commencement of the Glacial period. 



SECONDARY OR MESOZOIC PERIOD. 

 TRIAS. 



No trace of a fossil that I am aware of has been detected in 

 this formation in the South of Durham. In most of the bore- 

 holes the presence of a thick deposit of Rock-Salt occurs at the 

 base of the formation, the beds of which seem to rest on and to pass 

 gradually down and without any physical break into the upper 

 beds of limestone of the underlying Permian. It seems impos- 

 sible, from an examination of the cores of these bore-holes, to 

 divide the Trias of the South of Durham into an upper and 

 lower series, or to correlate it with beds of the same formation 

 further South in the Midland Counties, or West as in Lancashire. 

 Neither is it possible to correlate it with the divisions of the 

 German Trias. Formerly it was customary to assign the lower 

 part of this formation in Durham and Yorkshire to the Bunter, 

 but the more intimate knowledge afforded by an examination of 

 the numerous cores of the borings recently made in the South- 

 east oE Durham gives no support to this conjectured relationship. 

 It seems better to conclude that the red-shales and sandstones at 

 the mouth of the Tees represent a peculiar and local develop- 

 ment of the Trias than attempt to split it up into divisions that 

 have no exact representatives either in England or on the 

 Continent. 



PRIMARY OR PALEOZOIC. 

 PERMIAN = MAGNESIAN-LIMESTONE. 



The student is referred to the following works for information 

 on the Local Permian Eossils : — 



Catalogue of the Fossils of the Permian System, by R. Howse. 



Trans. Tynes. Nat. Field Club, Vol. 1. 

 Notes on the Permian System of Northumberland and Durham. 



Trans. Tynes. Nat. Field Club, Vol. 3. 

 Monograph of Permian Fossils, by Wm. King, Pal. Soc, 1850. 

 Mon. Brit. Perm. Brack., Pal. Soc, by Dr. Davidson. 

 Dyas, by Dr. H. B. Geinitz. Leipzig, 1861. 



