On the Physical History of the English Lake-District. 313 



new), and a new Gasteropod constituting a genus (Alycceodonta) 

 allied to Alycceus. A single palatal plate of Myliobatis or Zygobatis 

 (probably derived) was also fonnd. 



8. " On the Physical History of the English Lake- district, with 

 Notes on the possible Subdivision of the Skiddaw Slates." By J. 

 Clifton Ward, Esq., Assoc.E.S.M., F.G.S. 



The author traces the physical history of the lake-district from 

 the commencement of the period when the Skiddaw slate was 

 deposited. To this succeeded the volcanic Borrowdale series, which 

 is followed after a physical break by the Coniston Limestone. 

 Between this and the succeeding Silurian deposits there is little, if 

 any, break. Thus, in the Lake-district, the break between Upper 

 and Lower Silurian is physically below the Coniston Limestone, 

 though palaeontologically it is above it. 



The Old Red Sandstone period was one of denudation, which was 

 continued into the Carboniferous period ; and perhaps the whole 

 district was actually covered by the sea during the maximum 

 depression of the Lower Carboniferous epoch. Since then it has 

 probably never been submerged, but exposed to continuous subaerial 

 denudation. The physical significance of the Mell-Fell (Lower 

 Carboniferous) conglomerates receives special attention. 



The author then, from consideration of the amount of deposition 

 and rate of denudation, attempts to estimate the period which has 

 elapsed since the commencement of the record, and sets it down as 

 62,000,000 of years. The author then considers the age of the 

 Skiddaw slates. Erom 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 Elags. 



The palaeontological 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. 



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

 North Wales." By E. lluddy, Esq. Communicated by Prof. T. 

 M'K. Hughes, M.A., E.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 Cor wen) are described. Here occur the 

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

 level (probably) of the Hirnant Grit. 



