FOSSIL REPTILES. 341 



disturbed, give out an odour more or less strong of petroleum. 

 They are distinguished into several beds. The first is named 

 by the workmen^ the gross bed, or sulphureous stone. It is 

 from two to six feet thick, and does not divide into foliations. 

 The second is called white slate. It is four inches thick, very 

 argillaceous and soft, and divides into very slender laminae. 

 Plants, insects, and the first fishes are to be seen there. 

 Another schistus follows it, called small pieces, two feet thick, 

 divisible into thin leaves, composed, in a great measure, of the 

 debris of vegetables_, and containing many bivalve shells, ex- 

 cessively small, round, and pearly. 



The next bank is named thick pieces. It is a foliated lime- 

 stone, two feet thick, and exhibiting scarcely any traces of 

 vegetable debris. Then come two beds, scarcely two inches 

 high, named by the workmen black plates, which appear tinc- 

 tured by vegetable debris. 



The first white plate follows them. Flagstones for apart- 

 m.ents are made of this ; some large fishes are visible in it, 

 and fine dendrites. It is three inches high, and divisible into 

 thick leaves or slabs. 



At last comes the fishy plate, so named from the immense 

 quantity of fish which it contains, with small limnese. It is a 

 white limestone of a fine grain, with slender leaves, and of mo- 

 derate hardness. 



Under it is what is called the little skin, very thin, and of a 

 blackish grey. Then comes the third black plate, two inches 

 and a half high, which is followed by the knotted or Indian 

 stone. This is a grey, coarse-grained schistus, dotted and 

 radiated with white and yellow, and filled with fishes and other 

 animal and vegetable impressions. It is in much estimation, 

 and its thickness is about four inches. 



The mussel-stone is a blackish, micaceous limestone, full of 

 debris of vegetables, of small limnese, and of fragments of 

 mussels still pearly. It is about a foot in thickness. 



The dill strecken is a calcareous schistus, a little micaceous, 



