300 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. 13, 



the Ostrea vesicularis (associated, however, with the tertiary species 

 Ostrea gigantea, Terebratula semistriata and Cancer quadriloha- 

 tus), reposes on strata charged with Inoceramiis Lamar ckii and 

 Ananchytes ovatiis, which he beUeves to be the true representative of 

 the white chalk of Paris*. These, I would remark, are precisely the 

 relations which exist both on the northern and southern flanks of the 

 Alps. M. Delbos further indicates, that his second stage in ascend- 

 ing order, which had been also confounded with the chalk, is a lime- 

 stone characterized by Schizaster rimosa, Hemiaster complanatus^ 

 Nummulina millecaput {N. gigas, Catullo), Serpula spirulcea, most 

 of which fossils occur in the shelly eocene of the Vicentine. Lastly, 

 he points out, that although, even in his third or uppermost band, 

 the Ostrea lateralis and the O. gigantea of the lower beds are re- 

 peated, they are there associated with a profusion of tertiary species. 

 This band is the great receptacle of nummulites throughout the 

 neighbourhood of Bayonne, the Corbieres, &c., which nummulites (I 

 may remark) are all or nearly all of the same species as in the Alps. 



The facts developed by M. Leymerie are in my opinion essentially 

 the same as those described by M. Delbos ; for whilst he shows that 

 the "terrain a nummulites" is connected with the chalk by help of 

 certain fossils, still the great masses with nummulites are clearly 

 superposed. But then this author has a theory to account for his 

 *' terrain epicretace." Seeing that these supposed secondary rocks 

 of the south differ so much from those of the north of Europe, he 

 explains this in his last memoirf by supposing that they were de- 

 posited in separate and distinct seas ; so that certain animals may 

 have continued to live on in the one, which had ceased to exist in the 

 other basin. In this way he is inclined to think, that the nummulitic 

 rocks of the south may represent at the same time the upper part of 

 the cretaceous and the lower part of the tertiary system of the north. 



To this I would reply by positive data. It has been shown that 

 in this southern zone, and notably throughout the Alps, the very 

 beds of transition or union are positively underlaid by the true equi- 

 valent of the white chalk and a full complement of the cretaceous 

 system. Again, strata which M. Leymerie considers cretaceous, 

 merely from the presence of the Ostrea lateralis and the Terebra- 

 tula tenuistriata, are in my estimate the intermediate or transition 

 beds only ; and as the last-mentioned of these fossils is said to be un- 

 distinguishable from the T. caput serpentis, a species which mounts 

 high into the tertiary deposits, nothing is gained by such an argu- 

 ment, particularly when the most secondary or cretaceous of the two 

 species, the Ostrea lateralis, is stated to be associated with several 

 well-known tertiary species. 



In pointing out very clearly that the nummulitic rocks of Les Cor- 

 bieres are all posterior to the chalk, M. Talavignes^ has endeavoured 

 to divide the formation into what he calls two systems on account of 

 their unconformity ; but as no author has recognised a general break 



* Bull. Soc. Geol. Fr. vol. iv. pp. 557, 713. 

 t Mem. de TAcademie de Toulouse. 

 X Bull. Soc. Geol. Fr. vol. iv. p. 1127. 



