248 M. Bronghiart 07ithe 



sufficient exactitude. There are also found in the same 

 rocks belemnites, amnaonites, trochi, terebrae, serpulje, 

 smooth and striated terebratulce, &c. the complete enume- 

 ration and exact determination of which would carry me too 

 far from the principal object of this memoir. 



The greater part of the preceding shells are from the place 

 named the Perte du Rhone ; but they are not from the rock 

 analogous to the inferior chalk (green sand) which rests 

 upon it. 



This second rock, which is above that we have just 

 noticed and to a certain degree characterised, possesses a very 

 distinct and nearly horizontal stratification, dipping slightly 

 to the S.E. ; the thickest lower bed is composed of a yellow- 

 ish limestone, often shaded or veined by yellowish argillo- 

 ferruginous portions : it appears composed of an immense, 

 mass of lenticular stones, which were at first taken for num-^ 

 mulites), or a multilocular shell, but which have since 

 been recognised to be small madrepores, to which M. de 

 Lamarck has given the name orbitolites lenticulata. Above 

 are alternating strata of marly limestone and sandy clay 

 mixed with the green grains which are constantly found in 

 the lower parts of the chalk. 



This rock contains numerous organic remains, the resem- 

 blance of which to those of the green sand (craie chloritee) 

 struck me the first instant I saw them. This resemblance 

 long since struck M. Deluc (the nephew), and he re- 

 marked it to me when we examined in his collection the 

 pumerous organic remains of this rock, which have been 

 assembled by his uncle and his father. The analogy is still 

 more complete and apparent, when, as he has done, these 

 fossils are placed by the side of those of Folkstone in Eng- 

 land, which come from the green sand ; but they were still 

 more decisive when I was enabled to compare these shells 

 with those from Mount St. Catherine near Rouen. Yet 

 these relations are more real and easier to seize from their 

 general features than from a particular examination of these 

 bodies. Thus nearly the same genera are found in these 

 three situations, and the species so resemble each other that 



