PLATE XII. 



MICROSCOPIC APPEARANCES OF TRANSPARENT SECTIONS or CARBONIFEROUS AND 



PERMIAN ROCKS. 



Fig. 1. Carboniferous Limestone, Bakewell, Derbyshire, with Archaediscus Karreri, 

 Textularia, sp., and Valvulina, sp. Magnified 10 diameters. 



Fig. 2. Carboniferous Limestone, North Staffordshire, abounding in Endothyrce, 

 chiefly E. Bowmani. X 10 diam. 



Fig. 3. Carboniferous Limestone, Clifton, Bristol. An oolitic or concretional 

 limestone, largely composed of minute, radiated and laminated, calcareous spheroids, 

 sometimes nucleated, in rare cases Foraminifera forming the nuclei. The spheroids are 

 often more closely packed, but it would require larger space to show fully the oolitic 

 character of the rock. The Foraminifera are only represented in the drawing by a single 

 specimen of Textularia and a few Endothyra. X 10 diam. 



Fig. 4. Carboniferous Limestone, Clifton, Bristol. Amorphous or subcrystalline 

 rock, with Valvulina palteofrochus, V. decurrens, and Archcediscm Karreri. X 10 diam. 



Fig. 5. Carboniferous Limestone, Bangor. A subcrystalline rock, with Endothyra 

 Bowmani, E. ammonoides, and Texiularia, sp. X 10 diam. 



Fig. 6. Saccaminina-limestone (Carboniferous). A dark-coloured rock crowded with 

 segments of Saccammina Carteri. X 5 diam. 



Fig. 7. Upper Magnesian Limestone (Permian), Byers Quarry, Durham. An 

 opaque, very finely sandy rock, with sections of Dentalina communis and Trocliammina 

 incerta. X 20 diam. 



Fig. 8. Dark Permian Limestone (' Dunkler Kalkzechstein mit Productus horridus '), 

 Moderwitz, Saxe Weimar. A compact black marble with sections of Trochammina 

 pusilla and Nodosaria radicula. X 10 diam. 



Note. Figs. 1, 2, and 5 are from specimens kindly lent by Mr. H. C. Sorby, 

 F.R.S. Figs. 3 and 4 are from sections furnished by Mr. W. W. Stoddart, F.G.S., 

 and fig. 6 from one in the collection of Mr. J. Young, F.G.S. 



