﻿188 I)E. A. VATTGHAN ON THE PAI^EONTOLOGICAL [May I905, 



II. Detailed Description or Continuous Sections and Isolated 

 Exposures in the Bristol Area. 



(i) Continuous Sections. 



(a) The Avon Section. 



Tournaisian or Lower Carboniferous Limestone. 



M = Zone 1 of Modiola lata (MoDiozA-Zone) . 



Lithological character. — Shales with subsidiary limestones, 

 ending with a series of red limestones (Horizon a). 



Former designation. — The lower portion of the Lower Lime- 

 stone-Shales, ending with the ' Bryozoa-Beds.' 



Where exposed in the Avon section : — 



Clifton side : The cuttings on both the Avonmouth lines near 



Cook's Polly. 

 Leigh Woods side : A riverside exposure, and the cutting on the 



Portishead line. 



Coral-fauna. — None as yet recorded. 

 Brachiopod-fauna : 



f Cliothyris Royssii. 

 Abun- I Eumeiria (' Retzia') sp. 

 dant. 1 Camarotozchia aff. mitchel- 



y deanensis. 



[ Spiriferids (fragments of 

 Eare. < Spirifer sp. and Syringo- 



l thyris sp.). 



Other groups: 



Lam ellibranchi a . 



Modiola lata and M. sp. 



Sanguinolites spp. 

 Gasteropoda. 



Murchisonia spp. 



Bellerophon sp. 



j, [ Orthotetes crenistria. 



al e ' \ Leptena analoga. 

 And probably (see analysis of Stod- 

 dart's paper, p. 201) : — 

 Lingula sp. 

 (Discina) sp. 

 Chonetes cf. hardrensis. 



Bryozoa. 



Rhabdomeson cf. rhombiferum 

 and Rhabdomeson sp. 



Fenestellids. 

 Polychaeta. 



Spirorbis sp. 

 Ostracoda, several forms. 

 Scales of fishes and plant-remains. 



Note on the definiteness of Horizon a in the Bristol 

 area. — In so far as the brachiopod-fauna is concerned, Horizon a 

 is characterized by : — 



(i) The occurrence of forms which become enormously abundant in the 

 succeeding zone. Examples are: — Orthotetes crenistria, mut. K x ; 

 Leptena analoga ; Chonetes cf. hardrensis. 



1 It is pointed out, at the end of this paper, that the Modiola-Zone had 

 better be regarded as a shallow-water phase of the Cleistopora-Zone, than as 

 a distinct zone ; but the invariable occurrence of similar bathymetric con- 

 ditions, wherever the Upper Old Eed Sandstone is conformably overlain by the 

 Carboniferous Limestone, renders the distinction of this phase a matter of 

 considerable strati graphical importance. 



