and Recent Oalcareous Deposits. 51 
and recent calcareous formations. It should, however, be 
clearly understood that this term is only applicable to them 
both, as they undoubtedly present themselves to our notice, 
in connexion with occasional peculiarities depending upon 
conditions with which we are as yet very imperfectly acquain- 
ted. For example, the term “ Globigerine areas” has been 
employed by more than one eminent writer as synonymous 
with an ideal standard of what recent cretaceous mud ought 
to be like. It is not, however, in the purest Globigerine 
areas that the deposit approaching nearest to the Upper or 
White flint-bearing Chalk is being deposited. But that a true 
flint-bearing cretaceous rock is being very generally deposited 
over certain areas of the ocean, differing from it perhaps as 
much, in colour only, as the latter differs from the Grey, but 
nevertheless lithologically identical with it, is, I am inclined 
to believe, quite certain. On the other hand, grave objections 
have been urged against this view on purely paleontological 
grounds, which may be as insuperable as the authority is high 
of the eminent geologists who entertained them. But having 
had some practical experience in deep-sea exploration, and 
being aware of what has been done in this direction by others 
during the last ten or twelve years,|I cannot help considering, 
it somewhat premature to affirm—because ‘ not a single one 
of the characteristic Cretaceous genera of Mollusca, such as 
Ammonite, Baculite, Belemnite, &c., has been brought to light 
in the Globigerine areas, and nothing to indicate that the Creta- 
ceous formation (speaking in a geological sense) is going on 
anywhere with that sort of persistency which is inferred hy ” 
some *—that the attainment of this or equivalent paleonto- 
logical evidence is impossible. The fact is that no really 
appropriate means have heretofore been devised and _perse- 
veringly employed for determining the question ; and, looking 
at it froma less debatable point of view, the most that can 
be said of the opportunities heretofore available for the detec- 
tion of some of the missing paleontological links is—that the 
likelihood of their proving successful stands on a par with an 
attempt (were such to be indulged in by some zealous natura- 
list) to determine the precise nature and scope of the European. 
marine fauna by dropping a thimble at every mile ortwo miles, 
on the bottom of the area known as the British Channel.  _/ 
It will have been observed from the foregoing remarks 
that I have adopted as the basis of my conclusions the fact 
that, since the substance of the chalk itself furnishes un- 
* Extract from a letter of Sir Charles Lyell’s to the author, dated 
January 24th, 1870. 
4% 
