30 THE CARBONIFEROUS LIMESTONE OF BURRINGTON COMBE 
‘ Athyris ’ cf. gregaria. 
Rhipidomdla aff. Michelini. 
Orthotetes aff. crenistria. 
Productus semireticulatus (mutations). 
Productus aff. Cora (mut. C.) 
Productus 0. 
Chonetes cf. kardrensis. 
Chonetes aff. papilionacea. 
Chonetes cf. comoides. 
Chonetes papilionacea. , | j 
Subdivisions. 
(i) Horizon y. 
Already described in detail. This may also be regarded 
as the base of the main Syringothyris Zone. 
(ii) The Main Syringothyris Zone. 
This includes all the beds from Horizon y to the corner 
immediately beyond the Cave. 
Special faunal characters. 
Brachiopods. 
Spirifer aff. clathratus and var. are not uncommon 
just above Horizon y. They occur throughout the zone, 
but become more rare in the higher beds, and have not 
been recorded above the top of the main zone. 
Syringothyris cuspidata in the typical form attains a 
maximum and is everywhere common. 
Syringothyris aff. laminosa occurs throughout the 
zone but is never abundant. 
Reticularia aff. lineata occurs at a particular level 
near the top of the zone. 
Seminula ambigua is abundant at the top of the zone, 
just below Horizon and is associated with ‘ Athyris ’ 
cf. gregaria. 
