Vol. 62.^ LIMESTONE OF THE MENDIP AREA. 333 



Chonetes cf. papilionacea occurs very abundantly at numerous 

 levels throughout. Ch. cf. hardrensis is nowhere common, and does 

 not extend into the uppermost beds. 



The abundance of large gasteropods, of the genera Bellerophon 

 and Euomphaliis, is a very noticeable feature at certain levels in 

 this zone, particularly in the upper part. 



Kidwellian or Upper Avonian (Upper Carboniferous 

 Limestone). 



S = Zone of Seminula ficoides and its allies. 

 (SEMHVULA-Zone.) 



The lithological and palaeontological characters of this zone are 

 best treated under the separate subzones. 



S^ Subzone of Produclus cf. semireiiculatus, mut. Si. 

 (sEifixETicuLATUs-suhzone.) 



General lithological character. — Massive limestones, with 

 thin shale-partings frequently developed. The limestones are ex- 

 tremely variable in character ; locally, they are slightly dolomitic 

 in the lower part of the subzone. Hard, black limestones, with 

 abundant nodular and lenticular chert, form a very characteristic 

 feature in the uppermost part of the subzone. 



Special faunal characters: — 



This subzone is characterized by the association of certain 

 Clevedonian forms with the Lower Kidwellian fauna. 



Corals : 



Caninia cylindrica, mut. S T , occurs in this subzone. 



CyatJwphyllum <p is common in the lower part, and probably 

 ranges throughout. 



Lithostrotion Martini enters abundantly at the base, and is the 

 dominant coral throughout. 



Lithostrotion basaltiforme, var. brisiolense, occurs. 



Syringopora cf. reticulata still occurs, but S. cf. distans has 

 replaced it as an abundant form. 



Carcinophyllum mendijpense is highly characteristic of this sub- 

 zone ; locally, it is extremely abundant at the base. 



Cyathophylloid Clisiophyllids are not uncommon. 



Alveolites sp. is very rare. 



Brachiopods: 



Seminula ficoides and vars. occur very abundantly at certain 

 levels; but these forms are no more prominent than Athyvis 

 cf. glabristria, mut. S 1? which locally is extremely abundant at the 

 base, and A. cf. expansa, which ranges throughout and is abundant 

 at certain levels. 



Q. J. G. S. No. 246. 2 a 



