1852.] LYELL BELGIAN TERTIARY FORMATIONS. 349 



is a fissile slate more than half made up of siliceous sponge-spicules 

 (curved, straight, and forked) and siliceous casts of minute Foramini- 

 fera of the genera Textularia^ Nonionina^ Triloculina, Rosalina (a 

 species near to, if not identical with, R. Beccarii). This peculiar 

 siliceous schist or tripoli is of very slight specific gravity. Some si- 

 licified Wood and remains of Chelonians have also been found in the 

 associated stony layers at Dieghem. 



Beneath this siliceous schist, sands, 40 feet thick, with twenty-five 

 layers of gres lustre or grotto-stones, occur. The quantity of stone 

 in nodules seems to increase as we proceed northwards from Brussels, 

 but scarcely any fossils are found in it. 



[6 . ] Cerithium giganteum . 



This shell has been obtained from Aiflighem, near Assche (see Map, 

 fig. 1, PL XVI 1.), N.W. of Brussels, from a quarry no longer open, 

 which formerly furnished building-stone for the construction of a 

 neighbouring abbey. In the same stone are seen Lucina mutabilis, 

 Turritella intermedia, and Nautilus Burtini. Whether its position 

 was in II. of Table XII. (the Nmnmulites Icevigatus division) or in 

 III., I could not ascertain. 



3. Sands with Nummulites planulatus. Lower Nummulitic ; Middle 

 Eocene. (E. 3, Table I. p. 279, & IV. «, Table XII. p. 334.) 

 Systeme Ypresien, itage superieur, of M. Dumont. 



[1.] Loiver Nummulitic in the neighbourhood of Brussels. 



The only spot near Brussels, where I saw several bands of stone, 

 consisting of an aggregate of Nummulites planulatus, exposed in a 

 natural section, was about three miles south of the city, near Foret, 

 in a deep lane near the country-seat of M. Musselman (see Section, 

 fig. 8. I. p. 336, and Map, fig. 3. I. PI. XVII.). I examined this 

 section with Capt. Le Hon, and we observed there within a very 

 short distance all the strata from the lower nummulite-beds {N. pla- 

 nulatus) to the Laeken sands inclusive. At the bottom of the lane 

 several layers of stone are seen, containing casts of Cardium, Cytherea, 

 and other shells, which appear to underlie the nummulite-bed. But 

 this part of the section is obscure, and there are signs of disturbance, 

 as if a fault had brought down some strata higher in the series to the 

 level of the Lower nummulitic rock. The Nummulites planulatus 

 extends through a thickness of about 10 feet of sand, in part glau- 

 coniferous, and in the midst of which are some solid bands of aggre- 

 gated Nummulites. At a higher level the calcareous sands (III. a. 

 Table XII.) are distinctly seen, then the Nummulites Icevigatus bed, 

 separated by a thickness of 70 feet of strata from the lower sandy 

 and stony deposits containing N. planulatus. All the beds have a 

 decided dip, and are inclined at a steeper angle than any other 

 which I saw round Brussels. At a higher elevation, in the road 

 from Foret to St. Gilles, the greenish sands of the lower part of the 

 Laeken beds occur with Nummulites variolarius and other fossils be- 

 fore enumerated, p. 335. 



I have before stated that in the quarry at Schaerbeek an Artesian 



VOL. VIII. PART I. 2 A 



