108 
THE AVONIAN OF THE AVON GORGE 
and Bryozoans of several types can be collected at this level, 
but their accurate determination awaits much-needed research. 
= Subzone of Spirifer a if. dathratus. 
D i a,gn o si s : — 
Zafhrentis aff. Phillifsi is the only Zaflirentis. 
Spirifer aff. dathratus is enormously abundant. 
Fauna : — 
Corals : 
Zaphrentis aff. Pliillipsi. 
Brachiop ods : 
Productus cf. hurlingtonensis 
Chonetes cf. hardrensis. 
Orthothetes cf. crenistria. 
Leptaena cf. analoga. 
Rhipidomella aff. Michelini. 
Spirifer aff. dathratus. 
Syringothyris aff. cuspidata. 
Beticularia cf. reticulata. 
Athyris aff. glabristria. 
Camarotoechia mitcheldeanensis. 
Bryozoa and Crinoids are abundant. 
Palatal teeth of Elasmobranchs {Psammodus, etc.) are not un- 
common. 
Local detail: — 
Between Press’ Quarry and the Black Rock Quarry, the beds 
are exposed at the side of the line and most of the fossils cited 
above can be seen weathered out on the surfaces of the slopes. 
Camarotcechia mitcheldeanensis abounds in one of these beds 
and this is the highest level in the Avon sequence at which this 
Brachiopod is an important fossil. 
The best hunting-ground is, however, the lower 
Pls-ts III • 
portion of the Black Rock Quarry, in the beds 
which underlie the broad dip slope. 
Orthothetes cf. crenistria and the two varieties of Spirifer aff. 
dathratus occur in thousands ; Leptaena cf . analoga and Syringo- 
thyris aff. cuspidata are their commonest associates. 
Just below the slope, at the top of the Zi subzone, the sur- 
faces of the beds are often completely covered with the valves 
of Chonetes cf. hardrensis. Associated with this small species 
of Chonetes are the earliest examples of the group of papilion- 
aceous Chonetes. 
