THE CARBONIFEROUS LIMESTONE OF BURRINGTON COMBE 21 
throughout the series above the Bryozoa Bed ; especially 
at the top of the zone. 
Spirifer aff. dathratus and var. increase in abundance 
as we approach the top of the zone, and are very abundant 
at that level. 
Orthotetes aff. crenistria abounds at numerous levels 
throughout the series. 
Rhipidomella ah. Michelini is not uncommon in the upper 
part of the series, and increases in abundance towards the 
top. 
Camarotoechia mitcheldeanensis occurs throughout the 
series. 
Cliothyris glabristria and Productus cf. Martini are 
first recorded from the top of the zone. 
The same species of Eumetria which occurs in the 
Modiola Zone of the Avon Section has been recorded in 
the lower part of the zone. 
(ii) Differences. 
No specimen of Cleistopora has been recorded (in the 
absence of weathered surfaces this is not surprising). 
Spiriferina octoplicata is apparently rare throughout 
the series. In the Avon Section it is rare in the bassus 
sub -zone, but is highly characteristic of the octoplicata 
sub -zone, and attains a maximum at the top of this sub- 
zone. The failure to record it in any abundance at 
Burrington may quite likely be due to the absence of 
weathered surfaces. 
No specimen of Leptaena has been found. In the Avon 
Section, Leptaena occurs in the Modiola Zone and is abun- 
dant in the Cleistopora Zone. 
Orthotetes afi. crenistria and Spirifer aff. dathratus are 
not uncommon in the lowest limestones. In the Avon 
Section, these forms are rare in the Modiola Zone. 
Chonetes cf. hardrensis is abundant in the lowest 
