1852.] LYELL — BELGIAN TERTIARY FORMATIONS. 365 



Thecidea radians and Belemnites mucronatus, with TerebratulcB and 

 other characteristic fossils ; it contains also many rolled pebbles of 

 flint near its junction with the White Chalk. This fact is important, 

 as showing that the White Chalk with flints had sufl^ered denudation 

 previously to the deposition of the Maestricht beds. The occurrence 

 of rolled pebbles at the base of the Maestricht rock is analogous to 

 the pebbly glauconite which separates the Maestricht chalk from the 

 Lower Landenian, so that the parting layer of pebbles, which at Folx- 

 les-Caves might seem, at first sight, to aiford good ground for sepa- 

 rating the cretaceous and tertiary formations, loses all importance as 

 a line of demarcation. The upheaval and exposure of the secondary 

 rocks had evidently begun before the termination of the cretaceous 

 period. 



In the middle of the village of Jendrain above mentioned a chalk- 

 pit has been opened, where the White Chalk with flints is covered 

 immediately by the Lower Landenian containing the wreck of the 

 Maestricht chalk, and its flints or cherty rock, which consist of huge 

 flattened masses, several feet in diameter. At Wanzin (Map, fig. 2. 

 PI. XVIL), I saw several sections where the surface of the White 

 Chalk had been much denuded, and where the whitish glauconite or 

 tufeau of the Lower Landenian, characterized by Astarte incequila- 

 tera, filled up inequalities scooped out of the older rock. 



4. Orp-le-Grandy Pellaines, Lincentj and Amptieau. 



At Orp-le- Grand the light tufeau is quarried for building purposes 

 to a depth of more than 20 feet. One of the most conspicuous fossils, 

 called Gyrolites {Vermiculites of Nyst), resembles the tubular cavi- 

 ties left by a large boring Annelid, and traverses the stone in curves 

 several inches in diameter. The Astarte incequilatera connects this 

 rock with the glauconite before mentioned of Folx-les-Caves. The 

 Pholadomya Koninckii, also abundant, forms a link between it and 

 the glauconite of Tournay, before mentioned, p. 362. With these 

 shells I found a cast and impression of a large Scalaria, which appears 

 undistinguishable, so far as a cast will admit of comparison, with a 

 species in Mr. Bowerbank's cabinet from the Lower London Tertia- 

 ries or Thanet Sands. The other shells are Dentalium, casts of 

 Cucullcea, Area, Nuculay Turritella, Natiea^ and Pleurotoma ?, with 

 teeth of Lamna. 1 found also two species of Echinoderms, one of 

 them, according to Professor E. Forbes, of the genus Hemiaster, a 

 form belonging equally to the cretaceous and tertiary periods ; and the 

 other referred to Cardiaster by the same authority, who remarks that 

 this genus has hitherto been only met with in eretaeeous strata. 

 This discovery is interesting in its bearing on the question whether 

 the Lower Landenian fauna has most relationship with a cretaceous 

 or a tertiary type, or whether it be not intermediate in character and 

 in age. No Baculite, Belemnite, Ammonite, or other Cephalopod of 

 a family peculiar to the Chalk, has hitherto been met with in these 

 beds ; but the same may be said of the true cretaceous strata in many 

 regions. 



I visited Pellaines and Lincent, where magnificent square blocks 



VOL. VIII. PART I. 2 B 



