26 Rev. A. Sedgwick and Mr. Murchison on the Geological 



The lowest beds are thicker, of a lighter red colour, and pass into a hard and 

 nearly compact limestone, in which are many veins of a gray colour, and 

 numerous impressions of the larger valves of Producta Scotica ? 

 The fossils of these beds which fell under our notice consist of 



1. Producta lobata. T. 318, Min. Conch. 



2. horrida, T. 319 



3. Martini. T. 317 



4. latissima. T. 330 



5. spinosa ? T. 69 



6. ■ New species not figured 



1. Spirifer undulatus. T. 562 .. 



2. octoplicatus ? T. 562 



Encrinites, 3 to 4 species 

 Corals ? 



Other Localities. 



In the magnesian limestone, Sunderland ; and 

 also above the coal, Derby. 



Derbyshire. 



Anglesea and Devon. 



In Scotland only. 



Magnesian limestone, E. Thickley, Durham. 

 Ditto Ditto 



Below these fossil beds follows a succession of white sandstones of rather a 

 foliaceous structure, some of which however are amorphous and more com- 

 pact, with a subordinate bed of red iron-stone in a septarian form; which, from 

 being intersected by a number of cross fissures, resembles a tessellated pave- 

 ment, and is described by Dr. MacCulloch ; other associated beds consist of 

 white honeycombed sandstone, and layers of sandstone blackened with car- 

 bonaceous matter. For a very short interval the strata are not clearly dis- 

 cernible on the shore, through the accumulation of shingle and debris; but, im- 

 mediately to the north of the salt-pans, beds of white sandstone re-appear 

 (identical with those above described), overlying and alternating with blue and 

 black bituminous shales, most of which are highly calcareous, and full of en- 

 crinital stems and other organic remains. These latter pass into beds of regular 

 coal shale, two and three feet in thickness, in which are found the characteristic 

 plants, such as the PhytoUthiis verrucosus of Parkinson, reeds, and trunks of 

 arborescent ferns flattened; — in some of these beds coal was formerly worked *. 

 The alternations of shale and sandstone are continued for some distance, being- 

 succeeded by calcareo-bituminous shale, charged with Encrinites, and overly- 

 ing white sandstone. This sandstone forms the cover of a black calcareous 

 rock, perfectly analogous to some of the most common varieties of the mountain 

 limestone of England, Avhich contains throughout its mass many Productfe 

 (P. Scotica ?), a spiral univalve resembling Rostellaria, spines of Echinites, 

 Caryophyllia, Encrinites, and rarely an Orthoceras. This black limestone forms 

 * These vrorks have for several years been closed up. The best published account of them 

 may be seen in the work of Mr. Headrick, p. 212 — 219. 



