Reports and Proceedings — Geological Society of London. 329 



The value of the different zonal indices selected is discussed and 

 their distribution over the ai-ea is described. It is shown that, 

 whereas the zonal indices chosen for the larger groups of beds are 

 often sporadically distributed in the zone, the bands form remarkably 

 reliable horizons, extending frequently over large areas. 



The rocks are described under the following districts: — 



Shap and Ravenstonedale. 



Kendal and Kirkby Lonsdale. 



Arnside and Carnforth. 



Grange and Furness District. 



The Westmorland Pennines and Middleton in Teesdale. 



For purposes of detailed description, the Shap-Tlavenstonedale area 

 is taken as the type, and the other districts are briefly compared with 

 it. It is shown that in no one district is a complete development 

 of all the zones observed, and that it is only by taking a broad survey 

 of the whole area that the detailed faunal sequence can be definitely 

 established. 1 In the Shap area the Michelinia megastoma Zone is 

 scarcely represented, while farther west the fauna of this horizon 

 is one of the richest in the whole of the North-Western Province. 



The changes in the fauna of certain zones, when traced over large 

 areas, often depend more on the lithological characters of the rocks 

 and their modes of deposition than on the introduction of new forms at 

 definite horizons; thus, certain corals, such as Zaphrentis ennishilleni, 

 which is found to be associated with argillaceous deposits, characterize 

 different horizons in different districts. 



The deposits are shown to be for the most part of shallow-water 

 origin. The period of great submergence appears to have been during 

 the deposition of the Nematopliyllum minus Beds and the Lower 

 Dibunophyllum Beds. 



The lowest deposits are characterized by highly magnesian lime- 

 stones ; these appear to have been deposited under lagoon-like 

 conditions which encouraged the growth of calcareous algae, especially 

 Solenopora, and these in many places contribute largely to the 

 formation of the deposits. The majority of the limestones throughout 

 the series are rich in Foraminifera, and the more shaly layers in 

 Ostracods and Bryozoa. 



The silicifi cation of the organisms at many horizons in the sequence 

 is discussed, and the conclusion is arrived at that both silicification and 

 dolomitization of the limestones were practically contemporaneous 

 with the deposits in which they occur. The presence of spotted and 

 'brecciated' limestones is shown to be characteristic of the upper 

 portion of the Lower Dibunophyllum Zone. 



The movements which have affected the rocks in the Arnside district 

 have been the result of nearly horizontal thrusts, and it is shown by 

 means of zoning that the beds have, in places, been invei'ted and are 

 dipping at over 120°. 



1 Thus the lowest zones are practically absent from the Cross Fell area, since 

 the base of the Melmerby Scar Limestones represent an horizon high up in the 

 Nematopliyllum sub-zone : showing that the complete submergence of this 

 district did not take place until long after that of the area farther to the west. 



