20 THE CARBONIFEROUS LIMESTONE OF BURRINGTON COMBE 
special faunal characters of the various parts of this zone 
is, therefore, incomplete, and comparison with other areas 
is rendered difficult. 
The ‘ Modiola Shales ’ resemble the shales in the 
Modiola Zone of the Avon Section in lithological and 
palaeontological characters. These shales cannot, however, 
be separated as a distinct zone at Burrington. They 
alternate with limestones which contain many fossils, 
some in abundance, characteristic of the Cleistopora, 
fauna. Each series of these shales represents the pre- 
valence of a ‘ Modiola-Ostracod ’ phase. The limestones, 
which from the base of the zone contain a more or less 
characteristic Cleistopora fauna, indicate the gradual es- 
tablishment of the bathymetric conditions which prevailed 
during the formation of the Carboniferous Limestone. 
The ‘ Bryozoa Bed ’ exactly reproduces the lithological 
and palaeontological characters of the corresponding bed 
in the Avon Section. 
Special faunal characters : comparison with the Avon 
Section. 
(i) Resemblances. 
Cliothyris Royssii is common at two levels only, (1) 
in limestones near the base of the zone, (2) in the highest 
beds of the zone. This agrees with its abundance at two 
levels, in the Modiola Zone and at Horizon /3 respectively, 
in the Avon Section. 
A Productus of the type of P. hassus occurs in lime- 
stones a little above the Bryozoa Bed. This agrees with 
the occurrence of Productus hassus in the bassus sub-zone 
of the i\.von Section. 
Chonetes ‘ Buchiana ’ is abundant in that part of the 
series which is equivalent to the bassus sub -zone of the 
Avon Section. 
Chonetes cf. hardrensis is abundant at various levels 
