20 On the Older Floetz Strata of England. (Jury, 
ARTICLE V. 
Remarks on the Older Floetz Strata of England. 
By J. C. Prichard, M.D. F.L.S. F.W.S. &c. 
- (To Dr. Thomson.) 
SIR, 
I wave long entertained a suspicion that it may be possible by 
comparing the organic remains found in the lime-stones; which are 
connected with coal-fields, with those which characterize some 
other rocks, to elucidate the series. of secondary strata, which our 
island presents, and especially to determine the era of the inde- 
pendent coal formation. On reading Dr. Fleming’s late communi- 
cation on the fossils found by him in Linlithgowshire, 1 was so 
strongly confirmed in this persuasion that I have ventured to submit 
the following remarks on the subject to your inspection, and to that 
of the public if you think them worth inserting in your Journal. 
It seems improbable that a single species of organized beings 
should appear in one stratum, and then vanish entirely during an 
interval, and afterwards show itself again. It is contrary to what 
we find in nature. A fossil which abounds in one formation is often 
seen more scantily dispersed through a second, in a third it is 
scarcely found, and at length withdraws itself altogether from our 
view. A continual progress seems to have been made from the 
more simple to the more complex forms. We observe no retro- 
grade changes. But if the extinction and revival of a single animal 
be thus improbable, how much. more diflicult is it to suppose that 
an entire assemblage of co-existent beings should disappear alto- 
gether, that their place should be filled during an interval by crea- 
tures of a totally different character, and that these should become 
extinct to make way for a reproduction of the former class? The 
supposition is so contrary to the usual course of our observations, 
that I think we may conclude, when we discover two formations to 
abound with similar fossils, and a third to be characterized by re- 
mains of a different description, that the two former belong to one 
éra, and that the latter is either more ancient or more recent than 
both of them. If this conclusion be allowed, it will enable us to 
ascertain the relative age of the independent coal formation, or at 
least of the coal-fields in Britain. 
I shall first enumerate the extraneous fossils found in the oldest 
class of rocks which contains any, viz. those of the transition for- 
mation, and chiefly the transition lime-stone. 
Mr. Jameson mentions among the fossils of this rock encrinites, 
madreporites, tubiporites, corallites, and trochites. 
Von Buch found in the transition lime-stone of Norway, Sweden, 
and Finland, which lies under granite, a great abundance and 
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