INTRODUCTION. 107 



Werners " Transitional formations." But his subsequent visit to 

 the Alps and Jura mountains caused him to modify these views. 



He accomplished new and important work of investigation 

 in the Carboniferous districts of Belgium and the Rhine Pro- 

 vinces. He showed the extensive development of the highly- 

 tilted slate formation in the Ardennes, the Eifel and Hunsriick, 

 and pointed out that in the Rhine Province and in the Pala- 

 tinate (Pfalz) this formation had been penetrated by volcanic 

 rocks. The productive horizons were chiefly developed in the 

 northern French provinces, Artois and Boulonnais, while the 

 fossiliferous strata beneath the coal-bearing series were best 

 developed in the Hennegau. Thus Omalius d'Halloy laid the 

 foundation of geological knowledge over wide areas. His 

 more detailed works are those which deal with the Tertiary 

 deposits of the Paris basin. He united horizons 5 and 7 in 

 the classification system of Brongniart and Cuvier, and traced 

 the topographical distribution of each horizon. 



The hill of Petersberg, near Maestricht, was made the subject 

 of a local monograph of high excellence by Faujas de Saint- 

 Fond. The chalk series of this district has since been recog- 

 nised as the uppermost horizon (" Danian Stage") of the 

 Cretaceous formation, a stage absent in the British develop- 

 ment, but of very great interest from the intermediate 

 Cretaceous-Eocene character of the fauna. 



The monograph of Faujas de Saint-Fond begins with a 

 description of the hill and the deposits, more especially the 

 system of caverns and tunnels that had been excavated in the 

 rock. In the palaeontological portion, the first specimen 

 described is the huge reptilian skull, Mosasaurus Camperi, 

 that had bee-n found in these deposits in 1770. The specimen 

 originally belonged to a physician of the name of Hoffmann, 

 but, as the result of a lawsuit, it came into the custody of the 

 Canon Godin, and finally, after the siege of Maestricht by the 

 French in 1795, it was demanded as booty of war and trans- 

 ferred to the Paris Museum. The famous anatomist, Peter 

 Camper, had examined the jaw of a similar fossil animal and 

 identified it as the remains of a Cetacean, nearly allied to the 

 genus Physeter, whereas Faujas tried to demonstrate that it 

 represented a fossil crocodile. Both indications were proved 

 erroneous by Cuvier, who identified the remains as those of a 

 marine serpent-like reptile, and placed the genus Mosasaurus 

 among the lizards, in near relationship to the genus Varanus. 



