Vol. 65.] CARBONIFEROUS LIMESTONE OF COUNTY CLARE. 565 



The Zaphrentis Zone. 



The correlation of these beds with the Zaphrentis Zone of the 

 Bristol area is based on the following details of the faunal sequence 

 •common to the two districts. 



A. The clathratus subzone. 



1. The entrance of Zaphrentids at the base, but the absence of Za- 

 phrentis honincki. 



'2. The maximum of Phipidomella michclini, Productus cf. burling- 

 tonensis, and Spirifer aff. clathratus (the subzonal index). 



•3. The absence or rarity of Michelinia, C'aninia, and Syringopora. 



4. The absence of Schizophoria aff. resupinata and Syringothyris lami- 



nosa. 



5. The absence of Camarotcechia mitcheldeanensis, and Spiriferina 



octoplicata, except at the base. 



6. The abundance of Leptcena analoga and Syringothyris aff. cuspidata. 



B. The honincki subzone. 1 



1. The entrance of Zaphrentis honincki and its maximum at the 



summit, where it is associated with Canipophyllum cylindricum 

 and Caninia conmcopice (horizon y). 



2. The entrance and abundance of Michelinia and Syringopora. 



3. The entrance of Syringothyris laminosa. 



4. The development of a characteristic fish-fauna. 



5. The absence of Clisiopbyllids and Lithostrotion. 



The following points of difference are to be noted : — 



In County Clare Spirifer aff. clathratus is still abundant at the top of Z„; 

 but Schizophoria resupinata does not occur abundantly until the succeeding 

 -zone (compare the Mendip area). 



Amplexus is either absent or extremely rare in Z 2 . 



The thickness of this zone is about 800 feet, and it is thus 

 ■comparable with the development in the Mendip area, being more 

 than twice as thick as in the Avon section. 



The Syringothyris Zone.. 



The remarkable development of this part of the sequence in the 

 West of Ireland renders it impossible to compare it in detail with 

 any well-known locality in Great Britain. The unfossiliferous 

 oolites, shales, and dolomites of the Bristol area, which form so 



1 For the reasons for adopting this form as the subzonal index, in preference 

 to Schizophoria resupinata, see T. F. Sibly, Quart. Journ. Geol. Soc. vol. lxii 

 (1906) p. 355, and A. Vaughan, ibid. p. 301, footnote. 



