314 



SCIENTIFIC NEWS. 



thing of sea shells in any of the strata below the firat beds 

 of gypsum. Mr. Desmarest, of the Institute, is the only 

 person who had mentioned turbines and other fragments of 

 shells in the last beds of the third mass, which is the deep- 

 est; and their presence has lately been confirmed by his son 

 and Mr. Prevost. The first fragments of these shells are 

 discovered below what is called the great bed of gypsum. 

 The second, consisting of more species than the former, is 

 in a calcareous marie below what is called the Httle bed. 

 All the species to which these shells belong are found at 

 Grignon. They are calyptroe, murices, cerites, turritelloe, 

 volutes, ampuUarice, cockles, tellinae, cithereae, solens, cor- 

 buls?! &c. Beside these are found glossopetroe, vertebrte of 

 fishes, claws and shells of crabs, echini of the genus spatan- 

 gus, and consequently different from those of Grignon which 

 belong to the cypeastrse. Three small beds of gypsum, and 

 Bome strata of marie succeed, without any shells: and 

 lastly we come to a bed of calcareous marie, in the midst of 

 which is a bed of gypsum. Both these contain the same 

 shells. They are ceritce, which we may refer to the genera 

 petricolnm and tetebrale. In both the shell itself has dis- 

 appeared ; but in the first marie we find the figure of its 

 surface in relief, and the interior filled with raarle; and in 

 the second marie and the gypsum thereis a hollow moulded 

 by the outer surface of the shell, and a nucleus mould^ 

 by the inside of the shell, while the space occupied by the 

 shell itself is empty. Thus we have sea shells perfectly si- 

 milar to those of coarse limestone, not only in marie lying 

 between beds of gypsum, but in the gypsum itself. 

 Marie asstun- Messrs. Prevost and Desmarets have made another ob- 

 ing regular servation on the stratum of rnarle, that lies below the little 

 bed of gypsum, and which contains shells. They have found 

 this murle in certain spots affecting the shape of quadran- 

 gular pyramids, the faces of which are striated parallel to 

 the edges of the base. They noticed more than twenty of 

 these pyramids, some of which are as much as 3 cent. [1*18 

 inch] high, with a square base of 8 cent. [3*15 inches] each 

 way. These pyi'araids cannot be considered as halves of 

 - octaedra ; for their base is so confounded with the raarle, 

 that the opposite faces for completing the octaedra are by 



