548 MR. J. A. DOUGLAS ON THE [Nov. I909, 



IV. Generalized Description oe the Faunal Succession. 



Tournaisian or Lower Carboniferous Limestone. 



M.—Modiola Phase. 



Lithological characters. — Thinly-bedded yellow sandstones. 



Faunal characters. — These beds contain a rich lamellibranch- 



fauna, but no brachiopods characteristic of the succeeding zone 



have been recorded. 



Dr. Wheelton Hind has kindly examined the lamellibranchs 

 obtained from these beds ; he reports that they have a 'very Silurian 

 look ', but may be similar to those occurring at the base of the Car- 

 boniferous at Pinskey Gill in Westmorland. They may probably 

 be referred to Gramrnysia and Modiolopsis. 



It has been suggested by Dr. Vaughan that the presence of this 

 Modiola Phase, at the base of the Carboniferous Limestone Series, 

 indicates a conformable transition from the underlying Old Red 

 Sandstone. This point is of considerable interest, for the small 

 thickness and faunal characters of the Cleistopora Zone in this 

 district would suggest an unconformity. Throughout the whole of 

 County Clare, however, the exposures in these beds are so poor, that 

 there can be said to be no conclusive evidence. 



K = Zone of Cleistopora aff. geometrica (Czeistopoxa Zone). 



Lithological characters. — Olive-green and yellow sandy shales. 



Former designation. — Sandy basement-beds of the Lower Lime- 

 stone Shales. 



Faunal list : — 

 1 Orthotetes crenistria (YhiW.) mut.K^ | Camarotcechia mitcheldeanensis, 

 Leptcena cf. analoga (Phill.). Vaughan. 



Chonetes laguessiana, de Kon. Eumetria aff. carbonaria (Dav.). 



Spiriferina octoplicata (Sow.). Rhynchonella cf. acutirugata, 



Productus cf. bassus, Vaughan. de Kon. 



Productus sp. [precursor of Pr. pus- Reticularia reticulata, M'Coy. 

 tulosus, Phill.]. 



Special faunal characters: — 



The beds included in this zone have a thickness of not more than 

 20 feet. They contain an assemblage of brachiopods characteristic 

 of the Cleistopora Zone, but a further division into subzones was not 

 found practicable. 



The zonal index Cleistopora aff. geometrica has not been recorded, 

 but Spiriferina octoplicata and a bassiform Productus, the subzonal 



1 To avoid confusion, I have adhered for the most part to the terminology 

 used in Dr. Vaugban's paper on the Bristol area, although certain genera, 

 such as Orthotetes, Chonetes, Spiriferina, etc., are now undergoing revision. 



For reference to the work of Mr. R. G. Carrnthers on the Tournaisian corals, 

 see under the heading ' Correlation,' § VI, p. 564. 



