Geological Society of London. 377 



as 62,000,000 of years. He then considers the age of the 

 Skiddaw slates. From lithological resemblances he is led to cor- 

 relate the Skiddaw grit with the basement grit in the Welsh Arenig 

 series, and thus to regard the beds below the grit as the equivalent of 

 the Tremadoc, and perhaps of part of the Lingula Flags. 



The pal^eontological evidence for the correspondence of the Arenig 

 series with the whole of the Skiddaw slates rests chiefly on Graptolites 

 and Trilobites. The author holds that the evidence from the former 

 is inconclusive, and that from the latter to some extent contradictory, 

 so that the physical evidence can in no way be overridden by it. 



9. " On some Well-defined Life-zones in the Lower Part of the 

 Silurian (Sedgw.) of the Lake-district." By J, E. Marr, Esq. Com- 

 municated by Prof. T. M'K. Hughes, M.A., F.G.S. 



This paper treats of the zones of fossils occurring between the 

 Coniston Limestone and Coniston Grits, with a view of establishing 

 a boundary between the Cambrian and Silurian formations. In the 

 lake-district beds the genus Phacops is very abundant, one or more 

 species of its subgenera characterizing each fossiliferous formation. 

 The zones thus indicated are found to hold good when the organic 

 remains as a whole are considered. The author separates the Ash- 

 gill shales from the Coniston Limestone, giving separate lists of 

 fossils to show the palasontological difference, from which it appears 

 that but few (and those the very common Bala fossils) are common 

 to both, while the most characteristic Ashgill fossils do not occur in 

 the Coniston Limestone. They indicate that the Ashgill formation 

 is Upper Bala. It is very irregular in thickness, and the author 

 thinks this due to an unconformity above the Ashgill beds. Here 

 the author agrees with Prof. Hughes in placing the base of the 

 Silurian. He gives lists of the fossils in the basement bed and the 

 Stockdale Shales, and points out that their facies is distinctly 

 Silurian. Very few fossils are common to them and the Coniston 

 Limestone or Ashgill Shales. Hence there is here both a physical 

 and a pal^ontological break, so that the division between Cambrian 

 and Silurian should be placed at this horizon. A detailed description 

 (with lists of fossils) is given of the Coniston Flags and Coniston 

 Grits. An appendix contains some palaeontological notes on some 

 species of the genus Phacops. 



10. " On the Upper Part of the Bala Beds and Base of Silurian in 

 North Wales." By F. Buddy, Esq. Communicated by Prof. T. 

 M'K. Hughes, M.A., F.G.S. 



The author describes a series of sections in the upper part of the 

 Bala and the succeeding beds, and gives lists of fossils. Details of 

 the various beds between the Bala and Hirnant Limestone are 

 given, above which come soft blue shales underlying Tarannon 

 shales, when fossils cease until the base of the Wenlock is reached. 

 The author has been able to trace the Hirnant Limestone and grit 

 considerably beyond the limits of the Hirnant valley. The sections 

 at Cynwyd (to the west of Corwen) are described. Here occur the 

 equivalents of the Bala Limestone and beds above this up to the 

 level (probably) of the Hirnant Grit. 



