60 FeatherstonhaugK's Geological Report. 



the world where they occur, the series of clays and sands and 

 imperfect limestones which they exhibit, are so irregularly 

 distributed, that no one locality can be set up as a general 

 type. Formerly, their mineral character was principally 

 relied upon for their classification, but of late a new arrange- 

 ment has been applied to them, the basis of which is their sup- 

 posed proximity to the present order of nature, evidenced by 

 the respective proportions of fossil shells they contain of spe- 

 cies which exist at present. Of this a fuller explanation will 

 be given. 



Before any thing further is said of the lower division of 

 the tertiary, it is proper to remark that the opinion which 

 prevailed some time ago that there was a distinct sepa- 

 ration between the superior part of the chalk and the lowest 

 bed of the tertiary, as if geological causes had ceased for a 

 while, has been brought into doubt by more extended investi- 

 gations. It w^as known long ago that the surface of the chalk 

 had been greatly abraded, and the beds of plastic clay which 

 succeed to it in some parts of England are exceedingly loaded 

 with nodules of flint washed out of it. The deposite of Mont 

 St. Pierre, also in the Maestricht district on the continent, 

 which differs from the chalk and the lowest tertiary beds, 

 having a distinct mineral character, and containing fossils not 

 common to the chalk, showed a real passage from the chalk to 

 the tertiary. Similar observations have been made in other 

 parts of Europe. There is a most interesting paper connected 

 with this subject in the Transactions of the Geological Society 

 of London, vol. 3, part 2d, accompanied with plates of the 

 Gosau and Styria fossils, and a fine lithographic view of the 

 valley of Gosau, in the Salzburgh Alps, by Mrs. Charlotte 

 Murchison. In this paper Professor Sedgwick and Mr. Mur- 

 chison, after a careful examination of a series of beds lying 

 between the chalk and the tertiary, have, after a second in- 

 vestigation made by Mr. Murchison for that purpose, come to 

 the decision that a series of blue marls, alternating with com- 



