Environs ofLons le Saunter. 135 



The rock that appears to have been the last product of 

 the formation, is disposed in uninterrupted strata, the origi- 

 nal and very considerable mass of which has been more or 

 less deeply cut away in its upper part. 



The first strata often contain, to the height of 3 or 4 

 metres [nearly 10 to 13 feet], veins or bands of a kind of cal- 

 careous saudstone, which diminish in thickness as they rise, 

 and insensibly pass into the true gryphite limestone. It is 

 remarkable that these beds do not contain a single gryphite, 

 wherever this arenaceous limestone occurs, whilst, where it is 

 not found, thousands of gryphites immediately cover the 

 marl. 



At some feet from the arenaceous beds, the limestone 

 breaks easily into straight prisms ; the cast of the gryphite 

 detaches itself from the shell, and allows an examination of 

 the interior, where the impression of the muscular attach- 

 ment of the animal to each valve is distinctly recognised, 

 which rarely happens elsewhere. 



I shall lastly observe, that these shells are not mixed and 

 spread indistinctly over every part of these beds; the gry- 

 phites are principally assembled in innumerable quantities 

 at their junction ; the great ammonites are found laid on 

 their bases among the gryphites; the small ammonites are dis- 

 posed in groups with the belemniles, without eifecting a 

 fixed position in their thickness ; the others are less abun- 

 dant, and are placed in the neighbourhood of these groups. 



These beds are not equally provided with fossils ; some 

 are so full of them, that the shells compose the greater part 

 of their mass ; others, on the contrary, do not contain any, 

 or at least very few ; the latter are even and regular, the 

 former receive an uneven and tuberculous form from the 

 large shells that occupy their bases. 



