604 MR, E. D. VERNON ON THE GEOLOGr AND [DcC. I912, 



and the matrix is a coarse angular sand. In both the relative 

 proportion of pebbles to matrix is large, the pebbles are not evenly 

 bedded, and fragments of rounded red marl from the underlying 

 Keele Series are not uncommon. In each case the rock is very 

 calcareous. The pebbles have an average length of IJ inches, but 

 pebbles 3 inches long are quite common. Several kinds of rock are 

 represented among these pebbles ; arranged in the relative order 

 of abundance they are : — Carboniferous Limestone, Carboniferous- 

 Limestone chert, indurated and felspathic sandstones of Silurian 

 age, quartzites, and vein-quartz. 



In some of the conglomerates, especially the bed which crops out 

 at Corley Rock and again in St. Joseph's Avenue, Radford, near 

 Coventry, fossiliferous pebbles are not uncommon.^ 



The pebbles of Carboniferous Limestone yield various corals and 

 crinoids ; while, from the Silurian rocks, such fossils as the following 

 have been obtained ; — 



Bhynchonella nucula Sow. I Ortliis sp., cf. lunata (Sow.), 



Ehynchonella davidsoni M'Coy. | Ccelospira hemisiJherica (Sow.). 



The parent-rocks from which these Silurian pebbles were 

 derived must, therefore, have been largely of Llandovery and 

 Ludlow age. One of these Silurian pebbles, containing the last 

 fossil mentioned above, is a hard green sandstone very similar ta 

 the May-Hill Sandstone. 



The surface of the limestone pebbles, when unweathered, exhibits 

 a multitude of small cavities evidently caused by the grains of sand 

 that form the matrix of the rock, many of which still occupy 

 the cavities. Other larger depressions mark the points of contact 

 of adjacent pebbles. Such ' pitted ' and ' impressed ' pebbles are 

 invariably found to be limestone; they are everywhere common. 

 The ultimate cause of these pittings appears to be the great pressure 

 experienced by the rock, which has caused a partial solution of the 

 limestone at the points of contact. 



The relative proportion of Carboniferous Limestone in the con- 

 glomerates from two widely-separated localities is shown below : — 



Whitmore-Park Oidcroj) at 



Boring. Maxstoke. 



Carboniferous Limestone and chert 71 per cent. 84 per cent. 



Silurian and other rocks 29 ,, 16 ,, 



The average percentage of Carboniferous- Limestone pebbles is 

 thus about 75. 



With the exception of a few rounded and subangular pebbles 

 of quartzite and of vein-quartz of unknown age, the remainder of 

 the pebbles consist exclusively of Silurian rocks. 



In this connexion, it is of interest to note that llr. Horace 

 Brown (89) found that in the north, near Polesworth, the con- 

 glomerate contains only 9 per cent, of Carboniferous-Limestone 



' A detailed account of the fossiliferous pebbles from these conglomerates 

 will be given in a future paper. 



