364 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Maj 19, 



glauconite (G. 1) consist chiefly oiAstarte incEquilateralis, Nyst, well- 

 preserved and often with both valves united. On one of these I found a 

 small attached coral {Bendrophyllid) . In the same bed a large 

 species of Dentalium occurs, and some casts of Bivalves. 



Section at Folx-les-Caves. 



G I . Glauconite ; upper part clayey, with 

 small concretions 



20 exposed. 



No other member of the " Lower Landenian " is seen at Folx-les- 

 Caves, but a solid and whitish glauconite, called by Omalius d'Halloy 

 tufeau de Lincent, occupying a higher position in the same series, is 

 met with at the distance of three or four miles to the north and west, 

 as at the village of Jauche, where there is a hollow lane in which the 

 whitish tufeau and greenish sand or soft glauconite are seen to attain 

 a thickness of about 20 feet, and greatly to resemble in character 

 some members of the Chalk and Upper Greensand of many parts of 

 Europe. The tufeau is highly calcareous and of small specific gravity, 

 hence it is of cheap carriage and highly useful as a building-stone. 

 Some of the beds are cherty ; casts of a small Nucula {Leda) are 

 most common in the tufeau. In part of the region alluded to, 

 the Lower Landenian rests immediately on White Chalk with 

 flints without the intervention of the Maestricht chalk, as at Jen- 

 drain, and sometimes, as in the immediate neighbourhood of that 

 village and on the road from it to Orp-le-Grand, the Maestricht chalk 

 is reduced to a thickness of less than 2 feet between the White Chalk 

 with flints and the overlying Landenian. The Maestricht bed here 

 contains large concretions of silex, more or less pure, and is full of 



