T. Davidson — Continental Geology. 259 



Cosne (Nievre), of St. Julien de Peyrollaz (Gard), and it can scarcely 

 be dissimilar from the Cambridge Gault or Green Sand. 



''No. 9. — Cenomanien. The Gres vert Superieur (Upper Green 

 sand) is not found in our regions in the shape of sandstone, but it 

 seems replaced by the Vraeonien. The BJiotJiomagien stage is a marl 

 with Turrit, eostatus, Amm. rJiotJiomagensis, A. MantelU, etc., Inoceramus 

 striatus (but without Pecten asper), which du'ectly reposes upon the 

 Vraeonien." 



It will be observed from the tables and views already given, that 

 a marked difference of opinion prevails with reference to the pro- 

 priety of combining the Aptien and TTrgonien into a single stage, 

 M, Pictet and several other observers are of opinion that the latter 

 is in Switzerland everywhere entirely distinct from the Aptien, 

 while M. Coquand, Leymerie, and some others contend that the 

 two alternate in certain regions named by them. This subject -will 

 consequently require further study and confirmation. Again, certain 

 geologists would limit our Lower Green Sand to the Urgo-Aptien 

 stage, while others include part of it at least in the Neocomien. 



Some considerable difference of opinion has likewise been ex- 

 pressed, not only at home, but also on the Continent, as to the real 

 value or position of the well-known Cambridge Green Sand or Phos- 

 phate bed. Some consider it to constitute a portion of the Upper 

 Green Sand, while others would refer it to the upper portion of 

 the Gault, and abroad some geologists constitute it a distinct 

 stage, for which the term Vraeonien is proposed. I found this 

 identical Cambridge bed with the same water- worn fossils occurring 

 at Ese, a locality not far from the shore, between Nice and Monaco, 

 of which I will give a description in the sequel. It is a point of 

 great importance to determine the exact age of this Cambridge bed, 

 and in making a paleeontological comparison, there are several 

 points in the case which will call for especial caution ; and, as sug- 

 gested by Mr. Judd, we must in the first place determine whether 

 there are any derived fossils in the bed (so often met with in 

 beds of phosphate nodules). Secondly, can the distinctive cha- 

 racter of its fauna be accounted for without having recourse to 

 difference of age ? For this purpose it will be necessary to apply 

 the crucial test proposed by Edward Forbes, namely, whether the 

 same group of organisms (genus, sub-genus, etc.) is represented by 

 different species^ In the Geol. Mag.. vol. 3, p. 302, 1866, wiU be 

 found an interesting paper by Mr. H. Seeley, " On the Cambridge 

 Green Sand," to which the reader is referred ; and I understand that 

 the same gentleman has in preparation a work on the Geology of 

 Cambridge, in which this important subject will, I hope, be 

 thoroughly discussed, and that he will give us a complete list (with 

 figures) of the species peculiar to it.^ Another valuable paper " On 



^ Mr. J. F. Walker favours me with the following remarks : " You have called the 

 Cambridge phosphate bed, Upper Gault, although the people here caU it Upper Green 

 Sand. I have long douhted the determination. I think that it has been formed by 

 the denudation of the Gault. 1st. Because the common fossUs are Gault species. 

 2nd. The species characteristic of "Warminster are nearly absent. 3rd. The fossils 



