﻿Vol. 6 1.] SEQUENCE IN THE BRISTOL AREA. 263 



occurs in S ; and at Clee Hill it occurs soon after the close of the 

 Tournaisian. 



Notes on the Distinctness of the Tournaisian and Visean 

 Faunas^ tested by the Sequence in the Bristol Area. 



The following genera of corals occur in the Tournaisian, but do 

 not extend into the Visean : — Cleistopora and Zaphrentis. 



The following brachiopod-groups are confined to the Tour- 

 naisian : — 



Camarotoechia mitcheldeanensis. 



Productus cf. Martini. 

 Chonetes cf'. crassistria. 

 Chonetes cf. laguessiana. 

 Le.pt ena analog a. 

 Schizophoria resupinata. 

 Rhijridomella aff. Michelini. 



Eumetria spp. 

 Spirifer aff. clathratus. 

 Spiriferina octoplicata. 

 Syringothyris cuspidata. 

 Cliothyris glabristria. 1 



The following coral-groups are confined to the Visean 



Alveolites septosa. 

 Litliostrotion (all species). 

 The family of the Olisiophyllids 

 (including Lonsdalia). 



Cyathophyllum Murchisoni (type). 

 Cyathophyllum regium. 



The great brachiopod-group of the giganteid Producti is prac- 

 tically confined to the Visean (a few early forms of Productus Cora 

 are met with below). 



The following genera and gentes of corals pass up from the 

 Tournaisian into the Visean : — 



Syringopora: the only common Tournaisian circuius is Syringopora 9 ; the 

 circuli in the Visean are of ramulose and geniculate types. 



Michelinia : in the Bristol area I only know this genus in the Upper Tour- 

 naisian ; it may extend into the base of the Visean, where it is certainly rare. 



Caninia cylindrica : by its mutations this gens undoubtedly links the Upper 

 Tournaisian with the base of the Visean, and, on this fact, the Caninia- 

 Zone was originally founded. 



Amplexus is essentially characteristic of the Upper Tournaisian, but probably 

 extends, with Caninia, into the bottom of the Visean. 



Cyathophyllum <p is characteristic of the very top of the Tournaisian and of 

 the base of the Visean. 



The following genera and gentes of brachiopods pass up from the 

 Tournaisian into the Visean : — 



Productus, semireticulatus : this gens, by its mutations, constitutes a genuine 



link between the two divisions. 

 Chonetes papilionacea may be defined as a Visean form, which has already 



become important in the Upper Tournaisian. 

 Orthotetes crenistria is also a link of great importance ; but, whereas it is 



enormously abundant throughout the Tournaisian, it is rare in the Visean. 

 Seminula is an essentially- Visean genus, and is only found rarely at the very 



top of the Tournaisian. 



1 See note under Cliothyris glabristria, p. 298. 



2 Very few early forms have been found in C. 



t2 



