232 ME. T. ROBERTS ON THE UPPER JURASSIC ROCKS 



The fer sous-oxfordien includes the zone of Ammonites athleta, 

 A. ornatus, and the clays with pyritous fossils. The lower part of 

 the substage is formed of grey or brown calcareous clays, enclosing 

 numerous ferruginous oolitic grains ; its upper part consists of blue 

 or black clays containing crystals of selenite and pyritized fossils. 

 Its thickness is estimated at from 3 to 6 feet. 



The clays form low ground, and sections in them are rare. The 

 dark clays with pyritous fossils were seen at the river-side, a 

 short distance east of Soyhiere, and they also occur at Chatillon. 

 Similar beds, but considerably thicker, are exposed in the Combe 

 Chavatte, below Caquerelle, and they were also seen as far south as 

 Le Cernil, north of Tramelan. 



The clays in the upper part of this substage are precisely similar, 

 both in their lithological character and their fossils, to the Oxford 

 Clay of England. 



The following fossils were obtained from the localities given 

 below. It must be remembered, however, that this does not repre- 

 sent the whole fauna of these clays, but only the fossils collected 

 by us or presented to us by the geologists named in the intro- 

 duction. 



Fossils from " le fer sous-oxfordien". 





Glovelier 

 Tunnel. 



Chatillon. 



Combe 

 Chavatte. 



Soyhiere. 



Le Cernil. 



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The Occfordian rocks always occupy low fertile ground, and present 

 quite a contrast to the features produced by the overlying beds, 

 which usually stand out in bold relief, forming ridges supporting 

 a meagre vegetation. The hollows or valleys in which the Oxfor- 



