296 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 19, 



I may observe that all the shells occur in two beds, the united 

 thickness of which scarcely exceeds a foot, and the broken fragments 

 mixed with pebbles cause them to resemble shells thrown up on a 

 sea-beach. 



In the yellow, white, and green sands which underlie these Bolder- 

 berg beds, no shells have been found. They are referred by M. Du- 

 mont to part of his Rupelian system, but were it not for the acci- 

 dental preservation of the shells in the gravels Nos. 3 and 5, it would, 

 I conceive, have been impossible to separate the '^Bolderian" from 

 the overlying " Diestian/' or subjacent "Rupelian" strata. The 

 occurrence of glauconite, which in some countries would famish a 

 mineral character of considerable use in distinguishing formations, is 

 so universal in Belgium in every tertiary group as to afford no aid 

 whatever. 



In a visit of a few hours I obtained specimens of most of the shells 

 hitherto discovered, and the Bolderberg is the only locality where 

 any fossils of this peculiar fauna have been met with in Belgium. 

 The following list of 46 Mollusca and Corals is compiled partly from 

 my specimens, which M. Nyst examined and named, but chiefly from 

 information supplied by M. Bosquet of Maestricht. A large part, 

 however, of the remains are mere casts, and their determination is by 

 no means as satisfactory as could be wished. The notes of interroga- 

 tion express the doubts entertained by M. Bosquet or by myself on 

 the subject. 



lAst of Fossil Shells and Corals from the Bolderberg near Hasselt, 



1. Panopsea. 



2. Corbula pisum. Sow 



3. planulata, Nyst. 



4. Mactra; sp. not determined. 



5. TeUina ; allied to T. Benedenii of the Antwerp Crag. 



6. Donax Stoffelsii, Nyst. 



7. Lucina astartea, Nyst. 



8. Venus erycina, var. D., Nyst. 



V. erycinoidesly Bast. 



9. chionoides ?, Nyst. 



10. rugosa, Bronn ; so named for me by M. Nyst. 



11. — — similis?, Nyst. 



12. Venus; allied to V. incrassata, but more orbicular. 



13. Astarte radiata?, Nyst. 



14. Isocardia harpa, Goldf. 



15. Nucula Byckholtiana ?, Nyst. 



16. subglobosa?, Philippi. 



17. Leda interrupta, ^osg'. 



Nucula interrupta, Poli (Nyst). 



18. Pectunculus pilosus, Nyst. 



P. glycimeris, Lamk. 



19. Area latisulcata, iVy*^. 



20. Pecten Sowerbyi, Nyst. 



21. Ostrea; allied to O. Meadei, Sow., but different. 



