258 



mixed ; the oysters and pectinites are some- 

 times arranged in families. The whole are 

 easily detached, and their interior is filled with 

 fossil madrepores and cellapores (cellulaires). 

 Formerly, on examining the banks of sand- 

 stone, which at the northern extremity of Punta 

 Araya are frequently bathed by the sea, I had 

 thought, that some univalve shells, resembling 

 the genus helix, and mixed with sea bivalve 

 shells, belonged to the fluviatile species *. This 

 mixture is in fact found ^ in the lime-stone of 

 very recent formation, that covers the chalk in 

 the basin of Paris ; but in order to verify a fact 

 so important, we should have under our eyes 

 the fossile shells of Araya J, and examine them 

 anew with that scrupulous exactness, which has 

 been recently followed in this kind of investiga- 

 tion by Messrs. Lamarck, Cuvier, and Brong- 

 niart. 



We have just mentioned the mica-slates of 

 Maniquarez and of Chuparipari ; the formation 

 of the Alpine lime-stone of Punta Delgada, and 

 of Cocollar ; and that of sand-stone, of calca- 



* Reuss, Lehrbuch der Geognosie, t. ii, p. 441. 



t According to the interesting observation of Mr. Beudan. 

 (See Cuvier and Brongniart, 1. c. p. 89.) 



J Specimens of sand-stone, or shelly breccia of Araya, are 

 found among the geological series, which I sent in 1800 to 

 the collection of the king of Spain at Madrid. There are 

 none of them in the collections which we have deposited at 

 Berlin, and at Paris, 



