1852.] 



LYELL — BELGIAN TERTIARY FORMATIONS. 



295 



placed horizontally one upon the other. The following list of the 

 casts of fossils from the Diest sands, however imperfect, may at least 

 serve to show the present scanty state of our knowledge of this 

 deposit. 



Fossils from the Biest Sands 



of KesseloOy near Loiivain, 



1. Terebratula grandis, Blum» 

 T. variabilis, Sow. 

 T. Sowerbyi, Nyst. 

 T. maximus, Charlesworth. 





7. Cardium. 



8. Calyptrsea. 



9. Natica. 

 10. Trochus. 



2. Solen ensis ?, Linn. 





11. Buccinum. 



3. Syndosmya prismatica ?, W. Wood. 



Ligula donaciformis ?, Nyst. 



4. Axinus ? 



12. Fusus. 



13. Cerithium. 



14. Terebra. 



5. Mactra? 





15. Rostellaria. 



6. Pectunculus. 





16. Turbinolia? 



Bolderberg Sands (C. Table I. p. 279). 

 of M. Dumont. 



Systeme Bolderien 



Between Diest andHasselt, and about forty miles E.N.E. of Brus- 

 sels, a small ridge, running nearly N.E. and S.W., and rising to the 

 height of about 50 feet above the plain, and 200 feet, or rather less, 

 above the level of the sea, is called the Bolderberg (see Map). It is 

 situated about five miles N.W. of Hasselt, and its summit is formed 

 of the sands of Diest, already described, below which are some beds 

 of gravel and sand, of small thickness, in which the fossils exhibit a 

 marine fauna, quite distinct from that of the Antwerp crag on the 

 one hand, and that of the Limburg or Kleyn Spawen series on the 

 other. 



Fig. 1 . — Section of the Bolderberg. 



J 2. Diest sands and iron-sandstone. 

 C. Bolderberg sands and gravel. 



D. Limburg sands (Rupelien of Dumont), 



In the cutting of a road which traverses the top of the ridge in a 

 direction nearly east and west, and in other openings in the slope of 

 the hill, I saw — 



1. The ferruginous sands of Diest, with thin pipes of irony 

 sandstone, in horizontal beds ; the whole about 10 or 12 feet 

 thick. 



2. Next below, a light green glauconite and layers of brown sand, 

 with mica and quartz grains ; 2 feet. 



3. A bed of gravel, occasionally cemented into a conglomerate 



by iron, with numerous fragmentary and some entire shells 



this being the principal shell-bed of the Bolderberg forma- 

 tion ; 6 inches. 



4. Ferruginous and whitish sands ; 20 feet 



5. "Whitish sand and pebbles, with some shells, mostly in frag- 

 ments, and with numerous large Ostrece; occasionally cemented 

 into a conglomerate ; 6 inches ? 



