324 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 19, 



not entirely, in age with the Barton, Bagshot, and Bracklesham beds 

 of the London and Hampshire basins, and with the Sables moyens, 

 Calcaire grossievy and part of the Sables inferieurs of the Parisian 

 series. The two districts where I studied them principally were the 

 neighbourhood of Brussels and that of Cassel, in French Flanders. 



1 . Eocene Tertiary Strata of Cassel, near Dunkirk. Hill of Cassel, 

 Mont Noir, and Hill of Boeschepe. 



I shall first describe the Cassel district, because some of the Eocene 

 strata there occupy a somewhat higher position than any fossiliferous 

 strata older than the Limburg series known at present in other parts 

 of French Flanders and Belgium. 



The town of Cassel, situated about twenty miles S.S.E. of Dunkirk 

 (see Map, PI. XVII.), stands on the summit of a hill, 515 English feet 

 (157 metres) above the level of the sea. This hill rises on its north, 

 south, and west sides very abruptly from the surrounding plain, which 

 is about 400 feet below the level of the top of the hill. The railway- 

 station (K. fig. 4), at the western base of the hill, has been ascer- 

 tained to be 40 metres (131 English feet) above the sea. The Hill 

 of Cassel is the most western of a small chain which extends ten 

 or twelve miles in a south-easterly direction into Belgium, the town 

 of Ypres being situated near its eastern extremity. These hills are 

 all of very similar composition, geologically speaking, although the 

 Hill of Cassel displays, upon the whole, the greatest number of well- 

 characterized subdivisions of the tertiary series. It will be useful 

 therefore to consider it as a type, and to compare the others with it. 



Fig. 4. — Section of the Hill of Cassel. 



Les Recollets. E. 

 ..B2 



B 2. Diest sands. 

 El. ( e. Ferruginous sands (upper part of E 1 ?). 

 (Laeken< /. Sandy glauconite (middle part of E 1 ?). 

 beds). \,g. "Black band," with iVwrn. t)«Wo/ariw«. 

 F 2 "\ 

 ,„ ■ , l f ^- ^um. Icevigatus bed. 

 ( russeis f -^ ^^ Green marls and underlying sands, with Num. Icevigatus. 



E 3. Sands, clays, &c. Lower Nummulitic? 

 F 1. London Clay with septaria. Bored to a depth of 320 feet. 

 K. Cassel railway- station. 



beds). 



This hill, like all the others, is capped with ferruginous sands and 

 sandstone, doubtlessly belonging to the Diest sands (B. 2. Table I. 

 p. 279 and fig. 4), as usual barren of fossils. Their thickness at Cassel 

 cannot be measured, but on the summit of the hill of Mont Noir, near 

 Bailleul, about fourteen miles to the south-east (see Map, PI. XVII. 

 fig. 1), this formation is seen to be 20 feet thick. In that hill, which 

 is 430 feet above the level of the sea, the Diest sands consist, at 

 their base, of a conglomerate of flint-pebbles coated with hydrate of 



