THE CARBONIFEROUS LIMESTONE OP BURRINGTON COMBE 37 
sence of Productus 0, in the absence of Clisiophyllids and 
in its less fossiliferous character, i.e. Lithostrotion, Seminula 
and Productus afE. Cora are not so abundant in the lower 
part of the zone as in the upper part. 
Special faunal characters. 
Lithostrotion, Productus aff. Cora (mut. Sg), Seminula 
ficoidea and Chonetes papilionacea occur throughout, and 
abound at certain levels throughout the upper three- 
quarters of the zone. 
Productus aff. Cora (mut. Di) and Productus hemispheri- 
cus are common in the upper part of the zone. 
Productus 0 occurs at the base. 
Orthotetes and Cyathophyllum are rare. 
‘ Clisiophyllum ’ (Carcinophyllum) 0 is not uncommon 
in the upper part of the zone ; Dibunophyllum 0 has 
also been doubtfully recorded here. 
Comparison with the Bristol Area. 
If we except the wide overlap of the Syringothyris and 
Seminula faunas, which is so characteristic a feature of the 
Lower Seminula Zone in the Bristol Area, the main faunal 
characters of this zone at Burrington and in the Bristol 
Area are very similar. A detailed comparison is, there- 
fore, unnecessary. One striking difference should be 
noted. In the Avon Section, Lithostrotion and Seminula 
are extrernely abundant throughout the lower part of 
the zone ; at Burrington, however, these forms attain 
their maxima in the upper part of the zone, and are not 
abundant in the lower part. 
E. Dibunophyllum Zone. 
' d (f) Sub-zone. 
The base of this sub-zone, consisting of compact lime- 
stones with thin shale partings, is exposed in the limekiln 
quarry. 
