234 



MR. T. ROBERTS ON THE UPPER JURASSIC ROCKS 



The Terrain a chMtles siliceux is somewhat variable in character, 

 but is usually composed of hard, compact limestones, often siliceous 

 and separated by clayey beds ; its upper part is often oolitic. Dis- 

 seminated through the series are numerous nodules, which are 

 usually siliceous, and the fossils are sometimes silicified. 



The following sections, amongst others, were observed in the 

 rocks of this substage. At Thiergarten, near the south end of the 

 gorge, the 'Terrain a chailles silicon*' is seen to consist of coarse 

 bluish limestone with clayey partings ; some of the limestone bands 

 are nodular, and the whole' thickness of the series is about 98 feet. 



Pig. 1.— Section in Quarry near Roadside, south-east of Liesberg. 



Bathoniau. Nothing seen, pro- Oxfordian. Terrain a chailles Corallian 



bably Callovian siliceux. Oolite, 



and Oxfordian. 



A better section is shown in the quarry south-east of Lies- 

 berg (fig. 1). Overlying the Oxfordian are some thin beds of 

 yellowish limestone, succeeded by greyish limestone separated by 

 bands of dark clays, the whole being about 160 feet thick. These 

 beds are worked for hydraulic lime and are very fossiliferous. 



Similar beds were seen above Montmelon, and again on the east 

 and west side of St. Ursanne station. 



At the 1 Combe Chavatte,' further to the west, these beds are 

 more siliceous and contain silicified fossils. 



At Pichoux and again at Gobat the ' Terrain a chailles siliceux ' 

 is said to be wanting unless represented by some limestones three 

 metres thick, which form the uppermost part of the Oxfordian 

 (Greppin, o r p. cit. p. 66). 



The following fossils were obtained from rocks of this substage : — 



Locality, 



Belenmites hastatus. Blainv 



Ammonites cordatus, Sow 



convolutus. Quenst 



hecticus, Bein 



Pleurotomaria Munsteri. Bom } Liesberg. 



Pbasianella striata, Sow 



Chemnitzia keddingtonensis, Sow 



Nafica clymenia, cVOrb 



Pholadoruya paucicosta, Ay J 



