﻿186 PALJEONTOLOGICAL SEQUENCE IN THE BRISTOL AREA. [May 1905. 



The series of zones and subzones is as follows : — 



ZoiK 



^ DlBUNOPHYLLUM 



Seminula 



Syringothyris.. 



<! Zaphrentis 



M 



O 



H Cleistopora 



(31odiola--phsise) 



Subzones and Horizon: 



/ 



(D 2 ) Lonsdalia floriformis. 

 (D : ) Dibunopliyllum 9. 



(S 2 ) Productus Cora (mut. S 2 ). 

 (Si) Productus semireticulatus 



\ / (mut.) 



(C) Syringothyris aff. laminosa. 



(Z 2 ) Schizophoria reswpinata. 

 (Zi) Spirifer aff. clathratus. 



f (K 2 ) Spiriferina octoplicata. 

 \ (K x ) Productus bassus. 



(M) Modiola lata. 



(CANiNiA-Zor\e.) 



The correlation of the faunal divisions (enumerated in the fore- 

 going table) with the lithological divisions previously in use, is 

 fully set out in the detailed description of the Avon section (p. 188). 



The discussion of the reasons for choosing the zonal indices and 

 for dividing the whole Carboniferous-Limestone Series into two 

 great divisions can only be undertaken after the detailed account 

 of the whole area has been set out. The general scheme of 

 this detail is sufficiently explained by the Table of Contents 

 (p. 181). 



