the borrowdale series and the coniston flags. 483 



Discussion. 



Prof. Hughes regretted that the more important fossils were not 

 upon the table, as he thought an examination of them, or of the 

 matrix, might suggest some explanation of the difficulties. He 

 questioned the discovery of Orthis vespertilio, Trinucleus, tfcc. in the 

 Graptolitic Mudstones ; and with regard to the sections drawn by 

 the authors, he said he had not carried away quite the same im- 

 pression of the stratigraphical position of the beds in the area de- 

 scribed. He thought that the Coniston Limestone could seldom be 

 considered as one distinct mass of limestone, but that concretionary 

 bands of varying thickness and number appeared at various horizons 

 in a mass of shale in which different fossils locally prevailed at 

 different horizons. By this kind of evidence it was almost but not 

 quite certain that the Graptolitic Mudstones and their basement- 

 beds did rest on different parts of the Lower Series, e. g. at Skelgill, 

 on the limestone bands, and near Coniston, on the Ash-Gill Flags. 

 In the Craven district he had found a conglomerate at the base of 

 the Coniston-Ulag Series, but no Graptolitic Mudstones. In the 

 Sedbergh district a similar conglomerate seemed distinctly to 

 underlie the Graptolitic Mudstones. He allowed that the facies of 

 the Graptolites was very like that of the Lower Series, but pointed 

 out that Barrande had got the very same group in his E, e, i at the 

 base of his Upper Series. 



He further pointed out that there were in Xorth AVales two sets 

 of pale slates, one near the top of the Lower Series, the other near 

 the base of the Upper, and probably derived at second hand from 

 older volcanic rocks. Only the Upper were well marked in the Lake- 

 district ; and these were the Knock beds of the authors. 



Mr. De Kance stated that he had spent two years in mapping 

 the rocks of the Volcanic (Borrowdale) series underlying those under 

 consideration. He agreed with Prof. Hughes, that the fossiliferous 

 calcareous band referred to by the authors belonged to the Conis- 

 ton Limestone, and not to the underlying volcanic rocks, as stated 

 by them. And he remarked that in tracing the outcrop of the 

 Coniston Limestone across country, it was found to rest upon diffe- 

 rent and successive members of the underlying volcanic series, 

 which plunge under it with varying direction of strike and amount 

 of dip, the unconformity being so marked between the two sets of 

 rocks that occasionally the volcanic series appear to have obtained a 

 dip, been denuded, and faulted before the deposition of the over- 

 lying Coniston series. 



Mr. Hicks differed from Prof. Hughes as to the value of the 

 paper, which he regarded as at all events opening a question on 

 which other observers might be induced to bring forward their 

 views. He inquired whether Mr. De Eance's statements showing 

 unconformity at the base of the Coniston series did not conflict 

 with the views of Prof. Hughes. He thought that there was no 

 occasion to be surprised at repetitions of beds in such a district. In 

 some sections there is no visible unconformitv between the base of 



