80 L. M. Parsons— Carboniferous Limestone of the Wrekin. 



This faunal assemblage indicates definitely a D 2 horizon and 

 a fair similarity to the D2 fauna of the eastern typical facies of the 

 Derbyshire area worked out in detail by Professor T. F. Sibty. 1 



Among the more important points of this similarity is the 



presence of Alveolites septosa, Lithostrotion j'unceum, and Lonsdalia 



Jloriformis in the coral fauna of both districts. Species of Brachiopods 



common to the two areas are, Ifartinia glabra, Spirifer planicosta, and 



scabriculate Producti. 



On the other hand, the rarity of Dibunophyllum and the apparent 

 absence from the Wrekin district of other important Derbyshire 

 genera and species must be noted. I have not succeeded in finding 

 either at the Ercall or at Lilleshall the following important corals : 

 Cyathophyllum regium, Campophyllum derbiense, Lonsdalia duplicata, 

 and Zaphrentids. The absence of the last two named has a special 

 significance since they are found in Derbyshire towards the top of 

 the Lonsdalia (D2) sub-zone. It seems reasonable to infer that 

 "Millstone Grit " conditions succeeded those of the Carboniferous 

 Limestone in the Wrekin area during upper D2 times. 



With regard to the Brachiopod fauna, many of the Derbyshire 

 forms, particularly various Producti, are absent from the Wrekin 

 development, and another dissimilarity lies in the fact that in 

 Shropshire the corals predominate, whereas in the typical eastern 

 facies of Derbyshire both corals and Brachiopods are well represented. 



The Lilleshall Outcrop. 



The exposures of limestone seen at Lilleshall are situated at the 

 northern end of the village, where there are one or two disused 

 quarries, mostly overgrown. Examination is largely impeded by 

 water, but in a field near the post office there is a dry exposure. 

 All of these workings show about 25 to 30 feet of red mottled 

 limestone arranged in almost horizontal beds. Unlike the Ercall 

 limestones the Lilleshall material is not very argillaceous and 

 contains little interbedded shale. The most striking feature of the 

 limestone is its highly ferruginous nature. Analyses of this rock 

 give the following average composition : — 2 



Per cent. 

 Calcium carbonate . . . . . 66-8 

 Iron compounds . . . . .28-9 



Insoluble residue (silica) . . . . 3-8 



Traces of magnesium. 



99-5 



Thin sections of this material show that the iron compounds 

 consist mostly of interstitial hoematite, the introduction of which 

 occurred at a later date, and was probably connected with the Trias 

 which covers the limestone at the northern end of the Lilleshall 

 outcrop. Other points of penological interest are the absence of 

 dolomite and the presence of glauconite grains. 



Palseontologically, the Lilleshall beds are much poorer than those 

 seen at The Hatch. For this reason I give a separate faunal list as 

 follows : — 



1 Q.J.G.S., 1908. 



2 For this and other analyses I am indebted to Mr. H. A. Doy. 



