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Geological Society of London. 117 
portance of unconformity), should be the amount of organic 
change that we can trace to a connexion with the paroxysm. 
And yet what system of paroxysmal elevations has stood the 
trying test, when questioned on this principle? 
It is of the Middle Eocene epoch—that section of the lower 
tertiaries of which thé calcaire-grossier of the Paris basin 
may be cited as a central type and key-stone—that the Num- 
mulites are especially, and apparently exclusively, character- 
istic. The supposed carboniferous and oolitic Nummulites 
are of too doubtful a nature to be taken as exceptions. 
There is, itis true, a Nummulite (lV. intermedia) found in the 
Miocene beds of Piedmont, and another (NV. garansensis) in 
the Lower Miocenes of the Pyrenees. But I am not inclined 
to conclude with M. d’Archiac that these rare exceptions 
prove the existence of the last representatives of the genus 
after the Lower Tertiary fauna had disappeared, but rather 
to cite them in favour of the view that I have attempted to 
demonstrate, I trust successfully, when describing during the 
past year the Lower Tertiaries of the Hampshire Basin,— 
to the effect that the so-called Lower Miocenes are essenti- 
ally Lower Tertiaries and a portion of the true Eocene series, 
and that the passage from them into the Middle Eocene is 
perfect and gradual, when we have for our examination an 
area presenting a full sequence of deposits. | 
Nevertheless, it is not the less true that the nummulitic 
horizon is distinctly and definitely marked, and, from the 
frontiers of China and Thibet, even to the shores of the At- 
lantic, occupies a fixed position in the geological scale, a 
place above and succeeding the horizon of the lower tertiary 
lignites. The full demonstration of this great fact is a pre- 
cious gain to our science ; and when we consider what a vast 
area the nummulitic rocks occupy, what mighty mountains 
are made up of them, the prodigious accumulation of indivi- 
duals of the fossils from which they receive their appellation, 
and the readiness with which their age can thereby be deter- 
mined, we cannot but admit that the elucidation of their his- 
tory has been a boon of no small value to comparative 
geology. This great tertiary formation extends across 
Europe, Asia, and Africa, forming a zone of 98° of longitude, 
