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PKOCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 26, 



was unknown to M. Pictet at the time he published his work, I 

 here append the drawings I made in 1848 from specimens formerly 

 in the possession of the late M. Bouchard, which had been sent to 



Fig. 1. — Terebratula diphyoides. 



him by M. Malbos, from the compact limestone of Berrias (Ardeche). 

 I never could »see the necessity of burdening nomenclature by the 

 adoption of a distinct generic denomination for these shells ; and we 

 should not be zoologically warranted in supposing that because the 

 mantle or lateral portions of the valves have been more or less pro- 

 longed, we have therefore valid grounds for the creation of a new 

 genus, any more than we are warranted in separating Orthis hiloba, 

 Linn., from the Genus Orthis because the lateral portions of the 

 valves are more or less prolonged in a similar manner to what we 

 find in the deviating lobes of the valves in certain specimens of T. 

 diphyoides, T. viator, etc. 



It is very interesting to know that Mr. E. Tawney has discovered 

 a Diphyoid Terebratula in a block of ''Oxfordian age" in the Canton 

 de Vaud, and it is most probable that the shell is referable to T. 

 viator ; but in that case it would be very necessary that the true age 

 of the block in question should be accurately determined, so as to 

 feel certain that it also might not pertain to the age of the limestone 

 of the Porte-de-France. Nor must it be forgotten that M. Alphonse 

 Favre found a similar specimen at Yoisons, near Geneva, which is 

 described and figured in Pictet's work above named. In Switzer- 



