Mr. Prestwich on the Middle Eocene Tertiaries. 153 



of the Chalk in the rolled flints which form terraces round the hills 

 in Aberdeenshire. The probable continuity, therefore, of these beds 

 with those of the south of Sweden, where the same order of suc- 

 cession prevails, is inferred ; the extension of the Upper Greensand 

 so far north is a point of much interest. The Antrim beds are pro- 

 bably Lower Greensand only : at least their age is doubtful. 



6. ** On the Correlation of the Middle Eocene Tertiaries of 

 England, France, and Belgium." By J. Prestwich, Esq., F.R.S., 

 Treas. G.S. 



In a former paper the author had shown the correlation of the 

 strata beneath the Bracklesham series in England, the Calcaire 

 grossier and Lits Coquilliers in France, and the Upper Ypresiau 

 system in Belgium, and which he had proposed to designate as the 

 " London 7 ertiary Group," from the circumstance of these strata at- 

 taining the largest and most distinct development in the English area. 

 In the present paper Mr. Prestwich entered into an account of the 

 structures of the deposits next above. In France this is the Calcaire 

 grossier, which the French geologists have divided into four stages : 

 — 1. a lower one of green sands, with few fossils ; 2. a middle one, 

 of a calcareous freestone, abounding in marine organic remains 

 (Grignon, Courtagnon, and other celebrated localities being in beds 

 of this zone) ; 3. an upper division, of harder and more flaggy cal- 

 careous rock, rich in Miliolites and Cerithium, mixed with a few fresh- 

 water shells and the remains of plants and land animals ; and 4. a 

 series of white and light green marls, apparently of freshwater origin. 

 Each division attains at places a thickness of 30 to 40 feet, but the 

 lower ones are thickest in the centre and west of the Paris basin ; 

 whilst the upper ones, on the contrary, are thickest to the eastward. 

 The total thickness of the deposit, therefore, rarely at any one place 

 exceeds 100 feet, whilst the Upper Bracklesham series, with which 

 it corresponds, is more than 500 feet thick. This diff'erence the 

 author attributed to a more rapid subsidence of the English area than 

 of the French at that geological period. This, he showed, was accom- 

 panied by more marine conditions prevailing all through the English 

 deposit, and by the continuance throughout of the same green sands 

 which in France were confined to the lower division. That the 

 whole series was, however, synchronous with the Calcaire grossier 

 he considered proved by the circumstance, that, although the fresh- 

 water beds which existed in France did not extend to this country, 

 yet the organic remains of some of the beds of the Bracklesham 

 series gave evidence of one upper division higher than the beds with 

 the Venericardia planicosta and Cerithium giganteum of Bracklesham, 

 for at the latter place the proportion of shells ranging up into the 

 overlying Barton series was 30 to 100, whereas in some beds recently 

 discovered by Mr. F. Edwards at Bramshaw, and apparently at the 

 top of the Bracklesham series, the proportion is 46 to 100. The 

 middle beds of the Bracklesham series show the closest affinity with 

 the Middle Calcaire grossier, although there are only 140 species 

 in common. The lowest division of this series is more fossiliferous 

 in England than in France, showing a closer relation (43 to 100) 



