on the Geology of Constantine, I have received from M. Brossard several unpublished species; and M. Peron, who has intelligently explored the high plateaux of the provinces of Algiers and Constantine, has in his possession a great quantity of new materials, which he intends to make known, and which must certainly he very important, judging from the large quantities of Ostreoe which I have received from him for a publication upon which I am now engaged. In the chain of the Madonies in Sicily, I was able to recognize the Rhotomagian type of the environs of Tebessa, represented by identical fossils of the same colour (Ostrea syphax, Ostrea africana, Ostrea Overwegi, Coq.). M. Seguenza also discovered the Rhotomagian stage in the Province of Reggio, in Calabria. We know that it exists in the Lebanon, and in the desert which separates the Dead Sea from the Red Sea.
From the foregoing details it appears that, should we continue to take the English divisions as a frame- work for the general divisions of the chalk, we shall find it insufficient to contain the enlarged canvas.
We have indeed seen that beyond the basin of Paris the chalk of Mans is increased by a new stage (the Carentonian), the chalk of the west by three stages (the Angoumian, Provencian, and Dordonian), and the chalk of Provence by the Mornasian stage.
If we now endeavour to draw conclusions from the resemblance or identity of the faunas, we shall see that, in addition to the fossils which are common to all, and which form useful landmarks in the field of discovery, each region possesses species peculiar to itself; so that if we were to compare two extreme points, as, for example, Algeria and England, without taking into account the intermediate localities, we should be so struck by the great dissimilarities as to ask ourselves whether we are not comparing two different formations.
Fig. 4. — Section of the Cretaceous Beds of Algeria.
Tebessa. Dj. Osmer. Tenoukla.
But if we compare Algeria with Provence, Provence with the Charente, the Charente with the Sarthe, the Sarthe with Paris, and Paris with England, we recognize, without any surprise or shock, the connecting links which unite the scattered particles into a whole,
