President'' s Address. 81 



De Koniiick subdivides the genus Nautihts of the Car- 

 boniferous Eocks into nine sections or groups, according to 

 the external form, governed by the ornament, and other 

 characters,* viz. : — 



1. Globosi. 5. Disciformes. 



2. Atlantoidoi. 6. Lcnticulares. 



3. Serpentini. 7. Sulcifeii. 



4. Tuberculati. 8. Curiniferi. 



9. Ornati. 



The Distribution of the Mollusca from a Geological point 

 of view is a subject of much interest. So important a one, 

 however, cannot be treated properly in the small space at 

 our disposal, a mere passing reference must therefore suffice. 



The lowest division of the Carboniferous System in Scot- 

 land — the Calciferous Sandstone Series — is regarded, generally 

 speaking, as a deposit of fresh or brackish water origin. lie- 

 searches carried on of late years have revealed the presence 

 in this series of numerous bands of marine orimn, containino- 

 a fair preponderance of marine Mollusca. Scattered through- 

 out the Wardie shales we do occasionally meet with a few 

 bivalve shells, probably referable to Antliracoptera, or an 

 allied genus, without associated marine fossils, or other sur- 

 roundings of a marine nature. 



Definite horizons with marine fossils in the Calciferous 

 Sandstone of the East of Scotland were first indicated by tlie 

 late Mr J. W. Salter and other officers of the Geological Survey. 

 Thus, such a stratum was discovered at the Clubbiedean 

 Eeservoir containing a well-marked bivalve.-|- Again in 

 Berwickshire similar beds at Cockburnspath and Burn- 

 mouth yielded Athyris cmhigna, Modiola, Pteronites, Ed- 

 mondia nnioniformis, Aviculopecten, and Anthracomya.X 

 This bed, an impure limestone at Cockburnspath Cove, was 

 investigated by Messrs Gibbs and Salter, and was found to 

 be situated near the very hase of the Calciferous Series. § 



The finest development of the Calciferous Sandstone Group, 



* Famie Calc. Carb. Belg., 1871, pt. 1, pp. 90, 91. 

 t Mem. Geol. Survey, Scotl., No. 32, p. 144. 

 X Ibid., No. 34, 1864, pp. 43 and 57. 

 § Ibid., No. 33, 1866, pp. 28 and 73. 

 VOL. VII. F 



