S84 



THE GEOLOGIST. 



which polished and striated the subjacent rocks, transported many of the 

 erratic blocks, destroyed the pre-existing alluvium, and left much boulder-earth 

 in various places. 2ndly. To this succeeded a period of submergence, v^hen 

 the sea gradually advanced until almost the whole country was covered. This 

 was the time of the marine drift with floatiDg ice. The beds with arctic shells 

 belonged to it, and some of the brick-clays are probably but the fine mud of 

 the deeper parts of the same sea-bottom. 3rdly. The land emerged from the 

 water, during which emergence the preceding drift-beds suffered much denuda- 

 tion, giving rise to the extensive superficial accumulations of water-rolled 

 gravel that now overspread much of the surface. This movement continued 

 until the land obtained a higher position than it now has, and became connected 

 with the continent of Europe. Its various islands were probably also more or 

 less in conjunction. The present assemblage of animals and plants gradually 

 migrated hither from adjoining lands. Glaciers may have still been formed in 

 favourable places, but probably never regained the former extension. 4thly. 

 The land sank again until the sea in most places reached a height of from 

 tJiirty to forty feet above the present tide-mark. Patches of forest-ground 

 were submerged along the coast. The clays and beds of silt, forming the 

 " carses" of the Forth, Tay, and other rivers, were accumulated, as well as 

 the post-tertiary beds of the Clyde, &c., described by Mr. James Smith, the 

 shells of which agree with those of our present seas. 5thly. An elevation at 

 length took place, by which the land attained its present level. As Mr, Smith 

 has shown, this probably occurred before the Roman invasion ; but that man 

 had previously got into the country appears from the fact that the elevated 

 beds of silt near Glasgow contain overturned and swamped canoes with stone 

 implements. 



March, 14, 1860. — L. Horner, Esq., President, in the Chair. 

 The following communications were read : — 



1. "On the Occurrence of Lingida Credneri in the Coal-measures of 

 Durham," By J. W. Kirkby, Esq. Communicated by T. Davidson, Esq., 

 E.G.S. 



As the Lingnla Credneri of Geinitz, formerly known only in the Permian 

 rocks (Lower Permian of Germany ; Marlslate of Durham and Northumber- 

 land), has of late been found by Mr. Kirkby in the Coal-measures at the 

 Eyhope Winning, near Sunderland, he offers this notice as of interest both as 

 to the discovery of another species common to the faunae of the Carboniferous 

 and Permian eras, and as illustrative of some of the physical conditions which 

 obtained during the deposition of the Upper Coal-measures of the North of 

 England, the occasional occurrence of this Lingula proving that marine con- 

 ditions prevailed at intervals in the Durham area during the accumulation of 

 those deposits. 



The species now known to be common to the Carboniferous and Permian 

 faunae (besides L. Cred?ieri) are Terehratula Sacculus, Mart. {T. sujlata, Schl.), 

 Spirifera Urii, Elem. {Martinia Clannijana, King), Spiriferina costata, Schl. 

 {Si), octoplicata, Sow.), CamaropJwria Crumena, Mart. {Terehratula SchlotJieimii, 

 V. Buch.), Camarophoria globuUna, Phil. {TerehraUda rhomhoidea, Phil.), — on 

 the authority of Mr. Davidson; Ci/there elongafa, Miinst., C. inornata, M'Coy, 

 Bairdia gracilis, M'Coy,— on the authority of Mr. Rupert Jones; Gyracantlms 

 fnrmo.v/x, Ag. — according to Messrs. King and Howse ; Finites Brandli}?gi, 

 Jjiudl., Tri(joi/ocarpo)i, JS'oeggerafhi, Broug., Sigillaria reviformis, Brong., Cala- 

 mi.les appro.rimatus, Brong., and C. imcqvalis (?), Brong., — collected by Mr. 

 Howse in the lowest Permian sandstone. Erom the preceding list of Carboni- 

 ferous species found also in the Permian strata of Durham, we arc able (says 



