﻿Vol. 6 1.] SEQUENCE IN THE BRISTOL AREA. 217 



JFaunal character. — The beds composing (1), (2), (3), and (4) 

 have already been sufficiently discussed ; their fossils agree 

 precisely with those found at the same levels in other parts of 

 the Bristol area. 



The Better o]?hon-~Beds (5) are of great interest : firstly, 

 because they occur at a horizon which is unfossiliferous in 

 the Avon and Sodbury sections ; and secondly, because they 

 contain certain transitional forms between Cyathophyttum and 

 Caninia. The fossils found in these beds are 



Orthotetes crenistria (mut.). 

 Syringothyris cuspidata. 

 Syringothyris aff. laminosa. 

 Cyathophyttum (p. 



and at the top — 



' Chatetes ' tumidus (a bryozoan). 

 Bellerophon sp. (cf. costatus). 

 Euomphalus sp. 



Seminula aff. ambigua. I Productus sp. (cf. Productus 6). 



Seminula aff. ficoidea. \ 



For convenience of reference, I have adopted the title ' Better ophon- 

 Beds/ since Bellerophon is extremely abundant in certain of the 

 beds. Cyathophyttum f is also very abundant, and in chance- 

 sections is easily mistaken for Cyathophyttum Murchisoyii, a coral 

 which, in the Bristol area, is only common in the Dibunophyllum- 

 Zone. 



The abundance of this Cyathophyttum, combined with the fact 

 that specimens of Seminula and of a giganteid Productus can be 

 picked up on the stone-heaps in the quarries, at first led me to 

 believe that I was dealing with beds near the top of the Car- 

 boniferous-Limestone Series. But when I found that Orthotetes 

 occurred in large numbers, and that the characteristic Syringo- 

 thyris aff. laminosa as well as Syringothyris cuspidata were to be 

 frequently met with, it became evident that my first view was 

 incorrect. A very careful examination of the beds in place showed 

 that the Productus was only to be found in the very topmost beds, 

 and that Seminula was practically confined to the upper part of the 

 quarry, whereas Syringothyris aff. laminosa occurred near the base. 



I had also found the same beds in a quarry near West Ticken- 

 ham (see 'Isolated Exposures' p. 231), and a vertical section of the 

 Cyathophyttum seen in situ revealed the fact that the Eailand 

 Cyathophyttum is very different from Cyathophyttum Murchisoni 

 (the former shows as marked a relationship to Caninia as the latter 

 does to the Clisiophyllids). This view has been confirmed by the 

 sections which I have had cut from specimens of Cyathophyttum (j> 

 collected in the Eailand quarries. Hence, on palseontological 

 grounds, the Better op>hon-Beds must be assigned to the top of the 

 Syringothyris-ZoTie, immediately below the base of the Seminula- 

 Zone (that is, immediately below S x ). 



[It will be pointed out in the general summary that, if the 

 Carboniferous Limestone is to be divided into two great systems, a 

 lower (or Tournaisian) and an upper (or Yisean), the line of 

 separation must be drawn at the top of the Bellerophon-Beds.^ 



