d succeeding faunas. I need give only one instance,
namely, the manner in which the fossils of the Devonian system,
when this system was first discovered, were at once recognised by
palaeontologists as intermediate in character between those of the
overlying carboniferous and underlying Silurian systems. But each fauna
is not necessarily exactly intermediate, as unequal intervals of time
have elapsed between consecutive formations.

It is no real objection to the truth of the statement that the fauna of
each period as a whole is nearly intermediate in character between the
preceding and succeeding faunas, that certain genera offer exceptions
to the rule. For instance, the species of mastodons and elephants, when
arranged by Dr. Falconer in two series--in the first place according
to their mutual affinities, and in the second place according to their
periods of existence--do not accord in arrangement. The species extreme
in character are not the oldest or the most recent; nor are those which
are intermediate in character, intermediate in age. But supposing for
an instant, in this and other such cases, that the record of the first
appearance and disappearance of the species was complete, which is far
from the case, we have no reason to believe that forms successively
produced necessarily endure for corresponding lengths of time. A very
ancient form may occasionally have lasted much longer than a form
elsewhere subsequently produced, especially in the case of terrestrial
productions inhabiting separated districts. To compare small things with
great; if the principal living and extinct races of the domestic pigeon
were arranged in serial affinity, this arrangement would not closely
accord with the order in time of their production, and even less with
the order of their disappearance; for the parent rock-pigeon still
lives; and many varieties between the rock-pigeon and the carrier
have become extinct; and carriers which are extreme in the important
character of length of beak originated earlier than short-beaked
tumblers, which are at the opposite end of the series in this respect.

Closely connected with the statement, that the organic remains from an
intermediate formation are in some degree intermediate in character,
is the fact, insisted on by all palaeontologists, that fossils from two
consecutive formations are far more closely related to each other, than
are the fossils from two remote formations. Pictet gives as a w