28 THE CARBONIFEROUS LIMESTONE OF BURRINGTON COMBE 
Caninia cylindrica appears in the middle of the 
sub-zone and immediately becomes common. 
Spirifer aff. dathmtus and var. are abundant 
throughout. 
Syringothyris cuspidata in its typical form is not 
common below Horizon y, but attains its maxi- 
mum in the Syringothyris Zone. 
Schizophoria resupinata is apparently uncommon in 
the main sub-zone, but is common at Horizon y. 
In the Bristol Area — 
Michelinia only begins to be important in the upper 
part of this sub-zone. 
Amplexus characterizes the upper part of this sub- 
zone, and attains a maximum just below Horizon 
7 - 
Caninia cylindrica is common at Horizon y only. 
Spirifer aff. clathratus and var. are greatly dimin- 
ished in numbers. 
The typical form of Syringothyris cuspidata is 
abundant just below Horizon y, and here attains 
its maximum. 
Schizophoria resupinata is only common at the base 
of this sub -zone. 
(hi) Horizon y. 
At Burrington, Caninia cylindrica and Zaphrentis 
spp. are associated with Spirifer aff. clathratus 
and var. (abundant), Schizophoria resupinata 
(common), Cliothyris glahristria and Leptaena 
analog a. 
In the Bristol Area, these brachiopods are either 
absent or very rare at Horizon y. 
The above lists bring out very clearly the fact that we 
have at Burrington, as compared with the Bristol Area, 
a relative acceleration of the coral fauna on the brachiopod 
