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 *fr 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 %, 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.) 



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

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

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

 Mone of them in the collections which we have deposited at 

 Berlin, and at Paris. 



