184 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [NoV. 30, 



length into this svibject, it may be taken as proved that the pisolitic 

 limestones of Laversine, near Beauvais, and Vigny belong to an upper 

 member of the cretaceous series ; as they are stated by M. d'Orbigny 

 to contain Nautilus Danicus and Cidaris Forchhammeri in common 

 with the Faxoe beds, and their cretaceous origin is confirmed by other 

 authorities. The other masses of pisolitic limestone, in the depart- 

 ments of the Seine and of the Seine et Oise, may perhaps be of the 

 tertiary period. Without giving any opinion on that point, it is suf- 

 ficient for me to call attention to the existence of certain cretaceous 

 deposits near Paris above the Chalk containing peculiar species of 

 fossils, and for these we may use the term Terrain Banien, without 

 affirming that all the beds mentioned by M. d'Orbigny in the Pro- 

 drome, 23rd Etage, really fall into this category*. There are at 

 present very scanty means of comparing the fossils of the Terrain 

 Danien with those of Farringdon ; but when M. Hebert has published 

 the account of the pisolitic limestone, on which he is understood to 

 be engaged, that difficulty will be much diminished. 



Thus the examination of the whole list of species, or that of the 

 families separately, gives the result, that the Farringdon gravels con- 

 tain species hitherto thought characteristic of every bed from the 

 Lower green sand to the Maestricht sand inclusive ; but that those 

 referable to species found elsewhere above the Gault preponderate 

 nearly 10 to 1 in the number of species, and still more so in that of 

 individuals ; so that we need only consider to what part of the creta- 

 ceous series above the Gault this deposit belongs. This conclusion 

 limits our choice to the Upper green sand, or to a place altogether 

 above the Chalk ; for no one could seriously propose to place it on a 

 level with the Chalk. 



The outcrop of the Upper green sand through the counties of 

 "Wiltshire, Berkshire, Oxfordshire, and Buckinghamshire is too well 

 known to need description, except for the purpose of contrasting it 

 with the gravel of Farringdon : at Devizes its thickness is above 

 1 00 feet ; from thence it gradually diminishes in thickness as we 

 follow it to the eastward ; but throvigh all those counties the mineral 

 characters of the formation only vary between a fine sand, more or 

 less calcareous, with green particles occasionally hardening into beds 

 of stone, and a chalk marl. Nowhere is there any trace of gravel, 

 nor any ferruginous bed, in the Upper green sand of this part of 

 England. Very few of the organic remains of Fai'ringdon which are 

 referable to the Upper green sand, are found in that deposit in this 

 neighbovirhood. Warminster is the nearest spot which aff"ords any 

 large number of these species, and then only in the uppermost bed 

 of the formation ; but for the counterparts of the greater number we 

 must travel to the Tourtia of Belgium or to Essen in Westphaha. 



It might lead to erroneous results if we drew our conclusions from 

 the Bryozoa, which though now admirably described in France by 



* In a recent communication to the Academic Royale de Belgique, M. Hebert 

 asserts his conviction that the uhole of the pisoHtic limestone of the neighbour- 

 hood of Paris is synchronous with the Upper chalk of ]\Iaestricht. Bull, de I'xVcad. 

 t. XX. N. 3. 



