456 PEOF. E. J. GAEWOOD OX THE LOWER ( AKBONIFEEOrS [DeC. T912, 



During the progress of the work I have been indebted to many 

 friends and geological colleagues for much kind help. I have already 

 expressed my indebtedness to Dr. ^^larr and Dr. Yaughan, but am 

 glad of this opportunity of acknowledging also the assistance 

 received for some years past from students of University College, 

 London. Among many others, I am. especially indebted to Miss 

 Edith Goodyear, B.Sc, and Mr. H. S. Bion, B.Sc, P.G.S., my 

 assistants in the Geological Department at University College, who, 

 together with Miss Munro, B.Sc, Mr. P. de G. Benson, B.Sc, F.G.S., 

 and Mr. C. H. Cunniiigton, B.Sc, F.G.S. , have for several years past 

 accompanied me in the field. Without their ungrudging assistance 

 it would have been impossible to have acquired the detailed 

 information respecting the distribution of the zones set forth in the 

 accompanying maps and description. 



In the compilation of the fossil lists I am greatly indebted to 

 Dr. A. Smith AYoodward for the identification of the fish-remains : 

 and to Miss Madeline Munro for the determination of the many 

 forms of Bryozoa. The new forms met with during examination 

 of this material are described in the appendices to this paper. 



Finally, I should like to express my obligation to Dr. T. F. Sibly, 

 for his kindness in reading the typescript of this paper, and for 

 many valuable criticisms and suggestions. 



II. The Zoxal Divisions. 

 (A) The Athyris-glabristria Zone. 



This zone includes the beds from the Shap Conglomerate up to 

 the base of the Michelinia Zone, and, with the exception of the 

 beds which underlie the conglomerate in Pinske}^ Gill, contains 

 the oldest Carboniferous deposits in the North- Western Province. 



The index-fossil ranges from the base of the zone to the lowest 

 layer of the overlying Miclielinia Zone. It is found at several 

 horizons, and where present is generally abundant. ISo definite 

 variants of zonal value can be distinguished at the different levels.^ 



Lithology. — The zone is characterized by impure limestones 

 with occasional shaly partings. Many of the limestones are rich 

 in magnesium carbonate, some containing up to 40 per cent. The 

 magnesium carbonate appears always to be present combined as 

 dolomite, and the little rhombohedra of this mineral are well 

 seen in microscopic sections of the rock. The dolomitized beds 

 frequently contain abundant geodes of calcite and dolomite. 

 Many of the beds are porcellanous in texture, others are dun- 

 coloured and somewhat earthy, and these are usuall}' the richest 

 in dolomite. Towards the summit of the zone, the deposits become 



1 Dr. Yaughan, who has kindly examined specimens from one of the lower 

 horizons, reports that they include forms which are characteristic of Z 2 and 

 C respectirely in the Bristol District. 



