THE GEOLOGIST. 
JANUARY, 1859. 
ON THE NEOCOMIAN AND THE WEALDEN ROCKS IN 
THE JURA AND IN ENGLAND. 
By M. Jules Marcou, Professor of Geology in the Federal Polytechnic 
School, Zurich. 
In June, 1827, Dr. W, H. Fitton read before the Geological Society of 
London the following statement: — "It is obvious that, dui'ing a 
period of time sufficient for the accumulation of the Wealdeu, the 
deposition of matter in the adjacent seas could not have been 
inconsiderable ; so that we might expect to find, interposed between 
the strata which then formed the bottom of the sea and the Lower 
Greensand, a series of beds coeval with the Wealden in point of date, 
but differing fi-om it in possessing the characters of a marine deposit, 
and including marine shells and other productions of salt water ; with 
which, near the shore, the productions of the land, or even the fresh- 
water shells of the rivers, might be occasionally intermixed 
1st. That the Wealden and its marine equivalent could not both be 
found in the same place ; and consequently (since we have the former 
in England) that the marine beds of that date are not to be expected 
generally in this country ; 2dly. That the marine fossils of the beds 
cotemporaueous with the Wealden would probably be distinct, both 
from those of the Portland group beneath, and of the Greensands 
above them ; a consideration which gives peculiar interest to the 
fossils of this intermediate group." * Since that day, the Neocomian 
* See Observations on some of the Strata letwecn the Clialh and Oxford Oolite 
in the South of England. Transact. Geol. Soc. 2 Ser. vol. iv. p. 329. 
VOL. 11. B 
