RULES RESPECTING THE FOSSILS. 59 
'A 
I have in another place expressed my conviction 
of the impropriety, if not impossibility of making 
geological separations between our three fossilife- 
rous rocks. How far this view is supported by the 
similarity of their fossil contents in general ap¬ 
pearance, and in some cases by absolute identity, 
I have there shewn, and it remains for those of a 
contrary persuasion, to say if a gradual increase, 
and improved development do really exist in this 
series, —whether, progressing from the slate, proto¬ 
types can be detected.* Meanwhile however, till 
more accurate information regarding these reliques 
* An experienced collector at Plymouth, besides many other 
persons, are of opinion, that the fossils of the slate and sand¬ 
stone,—those at least in the immediate neighbourhood of the 
limestone, are properly speaking fossils of the latter rock, 
escaped as it were into adjoining strata from their own beds, but, 
this is admitting a statement fatal to their own doctrine of the 
separate ages of these rocks, since, the whole must have been 
fluid at one time to have allowed of this escape. It has appeared 
to me that, though the contemporiety of these three rocks is not 
supported by an universal identity of their fossils, it is far better 
in regard of their illustration to act as if separate investigations 
were altogether needed, since, nearly the whole may possibly be 
distinct from the others in each case.—That some few of those 
in slate and sandstone, in close connexion however to the lime, 
may be identical with the species occurring in the latter stratum, 
might I think be* most safely allowed, and should geologists see 
no objection to the coeval existence of three distinct fluids, and 
these separately inhabited by beings different in each case, then, 
the escape of some few sorts from the lime, into the slate and 
sandstone at the time of solidification, may in fact be a rational 
conclusion. The calamopores in slate might perhaps belong to 
the lime by this mode of reasoning. 
While however in addition to the fact, of fossils accumulating 
much towards the surfaces of beds and strata, it seems with us to 
be in great measure a rule that fossils of the slate and sandstone 
occur most abundantly where lime happens to be in the neigh- 
I 2 
