226 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



and Glauconie moyenne, is drawn up from the lists here referred 

 tor- 

 Total number Species ranging 

 of species. upwards*. 



D'Archiac (-(^e*»e) 188 108, — or 57 per cent. 



Melleville {Champagne) ... 273 166, — or 61 per cent. 



Graves {Oise) 318 162, — or 51 per cent. 



Adding the twenty-nine new species since described by M. Watelet, 

 and taking the mean of the above results, it would appear that 

 about 50 per cent, of the shells of the Lits Coquilliers (D'Arch.) or 

 Glauconie moyenne (Graves) lived on to the period of the Calcaire 

 grossier, whilst of the same fauna only about 16 per cent, were hving 

 in the older tertiary seas. 



On the foregoing evidence, therefore, I am inclined to agree with 

 those French geologists who would associate the " Lits Coquilliers " 

 with the " Calcaire grossier," rather than with the " Glauconie 

 inferieure." At the same time it cannot be denied that the Lits 

 Coquilliers and Sables divers form a very distinct and important sub- 

 division of that well-marked and typical higher group f. 



If we now turn to the London Clay, we find that so far as super- 

 position goes, it is exactly on the same geological horizon as the 

 Sables divers and Lits Coquilliers, but, instead of showing any close 

 palaeontological relations with this series, it exhibits almost entirely 

 different affinities. It is true that there are some well-marked 

 fossils common to both J, and that the London Clay shows more ties 

 with the Lits Coquilliers than with the Calcaire grossier, but still 

 the difference is great ; whilst at the same time its relations with the 

 Glauconie inferieure seem almost equally distant. These deposits 

 certainly present very different lithological characters, which might 

 lead to considerable variation in the fauna, but hardly to the extent 

 that here exists, or at least we must endeavour to ascertain whether 



* The downward range of the species is omitted, as M. d'Archiac gives no list 

 of the fossils of the Glauconie inferieure of the Aisne separately. In calculating 

 the number of species which range upwards, I have taken into account both M. 

 d'Archiac and M. Graves's lists of the Calcaire grossier fossils, as in each depart- 

 ment some species confined to the lower beds in the one seem to range higher in 

 the other. Taking only the Aisne, M. d'Archiac's lists show, including the un- 

 named species, but 71 identical species in the two deposits, while in the Oise 

 M. Graves makes the number of common species 155. 



t It is necessary to mention that this result is at variance with the opinion of 

 M. Al. d'Orbigny, who considers these deposits to be far more distinct ; so much 

 so that he only allows eight species of shells to be common to the two. He 

 admits that at the noted locality of Cuise-la-Motte there is a greater number of 

 Calcaire grossier forms, but he attributes that fact to the circumstance of many 

 of the fossils having been washed out of the older into the newer deposit, the 

 lithological character of the beds favouring such a transference. I should attach 

 more weight to this argument if the Calcaire grossier here contained species not 

 found elsewhere, but it is the Lits Coquilhers which is here distinguished by 

 the number of additional species. Cours elem. de Paleon. et de Geol. vol. ii. 

 p. 713, 727, & 731. 



X I have not been able to add many species to the eighteen I enumerated in 

 1847; after correcting a few errors in that list and adding some other species, 

 there are now twentv-five. 



