See papers by Darwin, Sharpe, Morris, and McCoy, in the
'Geological Journal'.] -- Tr'.
Although corals and Serpulidae occur in the most ancient formations
simultaneously with highly-developed Cephalopodes and Crustaceans, thus
exhibiting the most various orders grouped together, we yet discover very
determinate laws in the case of many individual groups of one and the same
orders. A single species of fossil, as Goniatites, Trilobites, or
Nummulites, sometimes constitutes whole mountains. Where different
families are blended together, a determinate succession of organisms has not
only been observed with reference to the superposition of the formations,
but the association of certain families and species has also been noticed in
the lower strata of the same formation. By his acute discovery of the
arrangement of the lobes of their chamber-sutures, Leopold von Buch has been
enabled to divide the innumerable quantity of Ammonites into
well-characterized families, and to show that Ceratites appertain to the
muschelkalk, Arietes to the lias, and Goniatites to transition limestone and
graywacke.*
[footnote] *Leop. von Buch, in the 'Abhandl. der Berl. Akad.', 1830, s.
135-187.
The lower limits of Belemnites are, in the keuper, covered by Jura
limestone, and their upper limits in the chalk formations.
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