of the Lake District. 



541 



Slates ; but tliey are not found in the Brafhay Flags, and the same 

 is true of a great portion of the other fossils, so that if the list of 

 fossils from Bannisdale Slates, Coniston Grits, and Upper Coldwell 

 Beds be examined, a large number will be found common to the 

 three. 



(4) The Coniston Grit fossils have a decided Lower Ludlow facies. 

 So much is this the case that Prof. Hughes remarks of the fauna of 

 the Winder grit " The prevalence of Rhynchonella;, especially B. nnvi- 

 cula, of Chonetes lata, of that round rather than elongated variety of 

 Orthis elegantula, known as 0. lunata or orbicularis, and other fossils, 

 would, in Wales, lead one to suspect that we were somewhere about 

 the passage beds from Upper to Lower Ludlow."^ It is true that 

 an explanation is offered in the Survey Memoir to account for an. 

 apparent Ludlow fauna in Wenlock strata, but if all these strata be, 

 as I am attempting to show, Ludlow, no such explanation is needed. 



(5) Monograptus leintwardinensis, occurring in the Bannisdale 

 Slates, was determined as a Lower Ludlow form by Mr. Hopkinson 

 in 1873.2 



An interesting point brought out by an examination of the Lower 

 Ludlow graptolite-bearing deposits of the North of England is the 

 great thickness of some of the graptolitic zones of these rapidly 

 accumulated shallow-water deposits, forming a marked contrast to 

 the thinness of the graptolitic zones of Llandovery age in the same 

 area. Thus we find the zone of Monograptus hohemiciis comprising 

 a group of strata having a thickness of about 5000 feet, whilst a 

 similar thickness is assigned to the strata of the zone of M. leint- 

 wardinensis. A list of the zones of the Llandovery-Ludlow rocks of 

 the area of the Lakes is appended, with the approximate thickness 

 of the beds of each zone. 



Equivalents 



in Silurian 



Keffion. 



Zone of 



Lower 

 Ludlow. 



"Wenlock. 



f Monograptus leintivardinensis 

 hoheniicus 



Nilssoni 



Cyrtograptus ilurchisoni .. 



I Gra-t/ae band .. 



Taeannon. I Monograptus crispus ... 



( turriculatus 



f Rastrites maxiinus 



Monograptus sjnnigerus .. 



cUngani hand .. 



Llandovery.' convolutus 



I . argenteus 



I fimhriatus 



I Dimorphograptus confertus 

 1 Diplograptus acuminatus . . 



Local Names. 



Bannisdale Slates 

 Coniston Grits 

 U. Coldwell Beds 



Middle 



Lower 



Brathay Flags .. 



Browgill Beds .. 



> Skelgill Beds 



Ft. in. 



5000 



5000 



1000 



1000 



to 22 



to 60 



25 



3 



3 



7 6 



8 



7 6 



to 25 



2 6 



1 Survey Memoir, Geology of the Country about Kendal, Sedbergh, etc., p. 16. 



2 Geol. Mag. Decade I. Vol. X. p. 519. 



