62 



PROCEEDINGS 



OF 



THE GEOLOGICAL SOCIETY. 



POSTPONED PAPERS. 



1. Om ^Ae " Caradoc Sandstone " o/" Shropshire. By J. W, 

 Salter, Esq., F.G.S., and W. T. Aveline, Esq., F.G.S. 



[Read June 15, 1853.*] 



The part of the country to which this paper particularly refers is 

 the tract lying between the Wenlock Edge on the east, and the Long- 

 mynd, Caer Caradoc, and the Lawley Hills on the west, extending 

 also northwards to the Wrekin, and the country about Buildwas on 

 the left bank of the Severn. When first mapped by the Geological 

 Survey, it was considered, in conformity with the views of the author 

 of the ' Silurian System,' that the whole tract was superior in posi- 

 tion to the Llandeilo flags, and that the ' Pentamerus (or 'Hollies') 

 limestone,' so well developed around the base of the Longmynd, was 

 the uppermost stratum of the formation called ' Caradoc sandstone.' 

 It was shown, however, in a paper read before the Society (Quart. 

 Journ. Geol. Soc. vol. iv. p. 298), that around the Longmynd these 

 upper portions of the Caradoc, or the Pentamerus beds, were alone 

 developed, the lower and typical portions being wanting f, and that 

 these upper strata reposed unconformably on the strata of Llandeilo 

 flags around the district of Shelve and Bishop's Castle. In a paper 

 lately read by Professor Ramsay (vol. viii. p. 162), the connection of 

 these ' Pentamerus limestones' and conglomerates with the base of the 

 Wenlock shale was fully expressed. It became necessary, therefore, 

 to re-examine the boundary-hne between the Caradoc sandstone 

 and Wenlock shale along the base of the Wenlock Edge, where the 

 ' Pentamerus beds' had been described (' Sil. Syst.') as forming an 

 intermediate or passage group from the Lower to the Upper Silurian, 

 and to draw the line at the base of those beds, if they should prove 

 distinct from the lower and more typical portion of the ' Caradoc' 

 It was also necessary to ascertain whether these ' Pentamerus 



* For the other papers read at this meeting, see vol. ix. p. 317. 



t The fossil hsts, too, appended to that paper indicated a large proportion of 

 Upper Silurian fossils mingled with those more peculiar to the formation, such as 

 the Pentameri, &c., and but very few Llandeilo flag species. 



