THE CARBONIFEROUS LIMESTONE OP BURRINOTON COMBE 41 
No subdivision of this zone is necessary. 
The establishment of a typical Visean fauna is exhibited. 
The lower beds are distinctly less fossiliferous than the 
upper ; in fact a true Seminula facies is first found at a 
considerable vertical distance above the top of Horizon 
The main zone shows all the characteristic faunal features 
of the upper Seminula Zone as developed in the Bristol 
Area. The topmost beds are relatively unfossiliferous. 
E. Dibunophyllum Zone. 
Only the basal beds of the 0 (p sub-zone, consisting of 
thin bedded limestones with thin shale partings, are satis- 
factorily exposed. Their faunal characters are exactly 
similar to those of the corresponding level in the Bristol 
sequence. 
In conclusion, I may draw special attention to the two 
most important features of the Burrington sequence as 
compared with the sequence in the Bristol Area. 
(1) The absence of shallow water conditions in Syringo- 
thyris time, as indicated by the absence of dolo- 
mites, which are so characteristic of the whole 
Bristol Area to the north. 
(2) Absence of any considerable overlap of the Tournaisian 
and Visean faunas, a feature which characterizes 
the lower Seminula Zone ( = semireticulatus sub- 
zone of Vaughan) in the Bristol area. 
