Geological Socieij/. 295 



may be pardoned for entering a record of my own views on a ques- 

 tion of no small complexity, and on which there is still much con- 

 trariety of opinion. 



During the past year we have been presented with several memoirs 

 describing formations superior to the chalk : which I shall also notice 

 in the order of the subjects, without any regard to the time when they 

 came before us. — In a Paper by Dr. Fitton on the structure of a por- 

 tion of the low countries in the north of France, among other inter- 

 esting details, is a description of three of this great class of for- 

 mations. He points out deposits in the neighbourhood of Calais, 

 Antwerp, and Tongres, which resemble the Crag of Suffolk. He com- 

 pares the sands of St. Omer, Cassel, and Lille, with the sands which 

 overlie the chalk in the London basin : and he states that the arena- 

 ceous beds of the hill of Cassel (like similar beds at Brussels) con- 

 tain large suites of fossils, generally agreeing with those of the Lon- 

 don clay. Lastly, he describes in detail the structure of St. Peter's 

 Mount near Maestricht, and shows that the inferior beds form a gra- 

 dual passage into the white chalk on which they rest; while the upper 

 beds bear marks of degradation and mechanical interruption, and 

 offer no indication of a passage into the superior sands. And he 

 adds that, out of more than fifty species of organic remains collected 

 by himself from this deposit, not more than ten are found in our best 

 catalogues of chalk fossils. 



I may here remark, that the suite of fossils in the Ca.ssel sands 

 throws no difficulty in the way of their comparison with the lower ter- 

 tiary sands and plastic clay of England, The terms London clay and 

 Plastic clay may be preserved as convenient mineralogical designa- 

 tions. They mark, however, nothing more than the subdivisions of 

 one great deposit between the lower and the higher members, in 

 which there is no line of zoological separation. In the London and 

 Paris basins, there is a great chasm in the order of succession between 

 the tertiary and secondary systems, which the labours of Geologists 

 may in time enable us to fill up. — The Maestricht beds are so nearly 

 related to the formation on which they rest, that they may be regarded 

 as the last term of a new series of deposits, which we hope hereafter 

 to find interpolated between the calcciirc grassier and the chalk. 



A Paper by Mr. Murchison makes us acquainted with the structure 

 of the tertiary formations on the southern flank of the Alps between 

 the Brenta and the Piave. They are divided into two great natural 

 groups exhibited in two i^ones : — an outer zone containing shells which 

 seem to be nearly identical with the well known fossils of the newer 

 tertiary Sub A|)ennine formations; — an inner and inferior zone con- 

 taining in its higher portions a few shells resembling those of a part 

 of the Bourdeau.\ basin, while its lower beds are distinguished by 

 innumerable organic remains, more than half of which seem to be 

 .specifically identical with those of the calcairc grossicr -or London 

 clay. These lower beds on the banks of the Brenta are inclined at 

 70'^ or 80', and are based upon a nummulite rock, which is abso- 

 lutely vertical, and conformable to the sraglia (containing ammonites 



and 



