112 
THE AVONIAN OF THE AVON GORGE 
time useless to attempt the study of the fauna in the section on 
the Clifton side of the river; a fossiliferous level in Ci is ex- 
posed on the opposite side of the river and will be described 
later. 
From the /ammosu-dolomites, at the foot of the Gully, good 
specimens of Orihothetes cf. crenistria have been obtained and, 
from the Ganmm- Oolite Quarry specimens of Michdinia cf. 
megastoma and Syringopora cf. reticulata were formerly col- 
lected in fair numbers. 
The upper portion of the zone, the Caninia shales and dolom- 
ites, has yielded no fossils on either side of the Avon Section. 
There is, however, a fossiliferous development of C2 as near as 
Failand. 
KIDWELLIAN OR UPPER AVONIAN. 
Seminula-ZonQ : S = 
Zonal index : — Seminula ficoides. 
Diagnosis : — 
The first abundance of Lithostrotion occurs at the base of the 
zone. 
The first abundance of Dihunophyllum occurs above the top 
of the zone, at the base of the succeeding zone. 
Lithostrotion Martini is the dominant coral throughout the 
zone and no Zaphrentis or Dihunophyllum has yet been recorded 
from the zone. 
Seminuloj 'ficoides is the dominant Brachiopod. 
Sj : subzone of Caninia cylindrica, mut S^. 
Diagnosis : — 
The Si subzone is characterized by the establishment of a 
dominant Kidwellian fauna (Lithostrotion, Seminula, etc.) with 
which are associated several mutations which are the direct 
descendants of Clevedonian forms (Caninia cylindrica, certain 
Producti, etc.). 
