L. M. Parsons — Carboniferous Limestone of the Wrekin. 79 



For the sake of convenience these may be termed the Ercall and 

 the Lilleshall outcrops respectively. Before considering the 

 Carboniferous Limestone in particular, we must note one or two 

 important facts concerning the district in general. 



The exact relation of the dolerite sill to the limestone above is 

 now somewhat obscured. The Carboniferous Limestone seen in the 

 area exhibits only a very thin development compared with that of 

 other districts in the Midland Province, and there are no strata 

 corresponding to "Pendleside" beds. The thin local development 

 of "Millstone Grit" is unconformable on the limestone; it rests 

 also upon older formations such as altered Ordovician material near 

 the Ercall. In the neighbourhood of The Hatch, south of "Welling- 

 ton, the Millstone Grit passes up into Coal-measures, though the 

 junction of these formations is often faulted as in the vicinity of 

 Lilleshall. 



With regard to the Carboniferous Limestone in particular, it will 

 be as well to consider the two outcrops separately, as there are 

 differences in petrology indicating somewhat different conditions of 

 deposit. 



The Ercall Outcrop. 



The limestone comes to the surface in a narrow curved belt 

 commencing at Steeraway, a short distance south of Wellington, and 

 extending southwards some distance beyond a place known as " The 

 Hatch". In the immediate vicinity of Steeraway the ground is 

 very much overgrown and only talus heaps mark the sites of former 

 workings. At this locality beds of Millstone Grit are seen, but 

 their relation to the limestone below is obscured. A mineral 

 railway passes from Steeraway southwards through dense woods to 

 The Hatch, where is situated the only good exposure of this outcrop. 

 Here the material is still being worked, and about 20 feet of thinly 

 bedded argillaceous limestones with shaly partings are seen dipping 

 at a small angle to the south-east. The relation of the limestone to 

 either the dolerite below or the Millstone Grit above is again 

 obscured. Petrologically the limestone is interesting on account 

 of the high proportion of argillaceous impurities and the presence 

 of a small amount of magnesium carbonate, which is not sufficient for 

 the formation of dolomite crystals. As far as faunal contents are 

 concerned these beds yield a fair number of specimens, which, 

 however, belong to relatively few genera and species, as the 

 following list shows : — 



Faunal List of the Ercall Limestone. 



CORALS. 



Syringopora cf. geniculata, Phillips. Diphyphylluma.it. concinnum, Lons- 



S. cf. reticulata, Goldfuss. dale. 



Alveolites septosa (Fleming). Lonsdalia floriformis (Martin). 



Lithostrotion junceum (Fleming). Dibunophyllum sp. 



L. irregular e (Phillips). 



BRACHIOPODS. 

 Athyris planosulcata (Phillips). P. scabriculus (Mai'tin). 



Martinia glabra (Martin). P. longispinus, Sowerby. 



Spirifer planicosta (M'Coy). P. latissimus, Sowerby. 



S. striatus (Martin). Chonetes cf. hardrensis, Phillips. 



Productus giganteus (Martin). 



