

«K 



In the southern area, roughly south of a 

 line drawn from about Dalton-le-dale to 

 Hetton, the Shell-Limestone rapidly passes 

 westwards into a series of well-stratified 

 beds, often profoundly altered, but not so 

 completely collapsed and brecciated as are- 

 the equivalent beds on the eastern side. 

 In the area under discussion the passage is 

 well seen in Castle-Eden Dene, where at 

 several points the beds are comparatively 

 unaltered, and yield a scanty but character- 

 istic fauna sufficient to fix their Middle 

 Limestone horizon. 1 They cover a very con- 

 siderable area of country in the southern 

 half of the county. In the northern area 

 both these beds and the uppermost Shell- 

 Limestones are wanting, presumably through 

 denudation. It will be seen then, that 

 despite the greater poverty of exposures, 

 the Permian succession is more complete 

 in the southern than in the northern part of 

 the county. (See fig. 3.) 



The Upper Limestones have not hitherto 

 been recognized upon the western side of 

 the ridge ; on the eastern side, however, 

 matters are different. Here we find the 

 various members of the Upper Limestones 

 both overlying and flanking the side of the 

 Shell-Limestone, which in elevated visible- 

 sections slopes very rapidly down to the 

 sea-coast, corresponding to the original 

 eastern side of the reef. 



Whether or no the Upper Limestones 

 were ever deposited west of the Shell-Lime- 

 stone reef is still an open question. In 

 Hesleden Dene and at Blackball Colliery, 

 for instance, and presumably at Hartlepool, 

 they certainly overlie the Shell-Limestone : 

 but a common position for them, especially 

 evident in the shore-sections, is down 

 upon the eastern side of the bank of Shell- 

 Limestone. 



The Upper Limestones may, of course, 

 have been deposited in part upon the flanks 

 of an elevated ridge or reef of Shell-Lime- 

 stone, in which case one might reasonably 

 expect to find derived fossils of the Shell- 

 Limestone included in the Upper beds. ]N"o 

 fossils have yet occurred to my knowledge 

 in the highly-altered Middle Limestones on 



1 A list of the fossils found in these beds is tabu- 

 lated in the last column on p. 215. The most 

 interesting form is Astartc vallisneriana King, 

 hitherto recorded only from the Lower Limestone 

 at Whitby. 



