246 MR. T. ROBERTS ON THE UPPER JURASSIC ROCKS 



Pterocerian Fossils. 





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Chenmitzia Bronni, D 'Orb 





































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Pholadornya Protei, Aq 





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Homoinya hortulana, D' Orb 





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Trigonia supraiurensis, Aq 







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Modiola subsequiplicata, Goldf. 





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The Virgulian is exposed in the ' Combe Grede ' as a thick series 

 of greyish, compact limestones, with some marly beds. At Brenets 

 there is at the base of the Portlandian a marly bed which has yielded 

 Exogyra virgula. Further south, owing to the absence of this 

 fossil, it has not been recognized with certainty, although the marly 

 bed, which is more or less persistent at the base of the Portlandian, 

 may probably represent it in part, at least. According to Jaccard, 

 however, the Virgulian is said to be wanting, and the term " Port- 

 landien" is used by him to include all the beds between the base of 

 the Purbeckian and the top of the Pterocerian in the Jura Yaudois 

 and JSTeuchatelois. 



The lower division of the Portlandian consists of massive grey 

 and compact limestones, which are largely quarried. Towards the 

 base these beds are lighter in colour and become marly. Fossils 

 are never abundant in these rocks, but they nevertheless contain 

 fragments of teeth, scales, and bones of fish and other vertebrates. 



The upper Portlandian is largely made up of massive limestones, 

 which are often dolomitic, and distributed throughout it are beds of 



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