﻿Vol. 6 1.] SEQUENCE IN THE BRISTOL AREA. 193 



y= Horizon 7. 

 (The top of the Zaphrentis-Zone and the bottom of the 

 Syringothyris-Zoiae.) 



Where exposed in the Avon section : — 



Clifton side : The southern end of the present Black-Hock Quarry. 

 Leigh Woods side : Towards the top of Quarry 2. 



Special faunal characters : — 

 Erachiopods : 



SyringotJvyris cuspidata, S. aff. laminosa, and Orthotetes creni- 

 stria, muts. Z and C, are common. 



Chonetes papilionacea becomes abundant and Chonetes cf. 

 hardrensis rare. 



Productus aff. semireticulatus is occasionally found. 



All the other brachiopods cited as typical of the Zaphrentis- 

 Zone are rare at this horizon. 



Corals : 



Michelinia and Ampleocus are not uncommon, but the important 

 feature of the horizon is the co-occurrence of Zaphrentis and 

 Caninia in remarkable abundance. The level is thus a well- 

 marked ' horizon of overlap ' of the Zaphrentis- and Caninia- 

 Zones, and is consequently designated Horizon y. 



C = Zone of Syringothryis aff. laminosa = Lower 

 Caninia -Zone. (STBiwGOTHYSis-Zone.) 



Lithological character. — The following rocks are met with 

 in ascending order : 



(1) Encrinital limestones, which are appreciably dolomitic. 



(The laminosa-dolomites.) 



(2) A thick band of oolite. (The Caninia -Oolite.) 



(3) Shales with thick bands of dolomite and subsidiary beds 



of oolite (lower part only). 



Former designation. — In ascending order: 



(1) Top beds of the Lower Limestone. 



(2) Gully Oolite. 



(3) Middle Shales (lower part only). 



Where exposed in the Avon section : — 

 Clifton side : 



(1) Occurs between the Black-Hock Quarry and the Gully- 



path and at the base of the Gully Oolite-quarry. 



(2) Forms the main portion of the Gully Oolite-quarry. 



(3) Is exposed in the low railway-cutting between the Gully 



and the Great Quarry (lower part only). 

 Leigh Woods side : 

 The topmost beds of (1), (2), and the very lowest beds of (3) 

 are seen in Quarry 3. 



