regards their animal and vegetable inhabitants. By this it means
that the two regions have a very large number of forms peculiar
to themselves, and which are supposed not to have been derived
from other quarters during modern geological times. Each may be
considered as a centre of distribution in the latest process of
dissemination of species over the surface of tropical America.
Para lies midway between the two centres, each of which has a
nucleus of elevated table-land, whilst the intermediate river-
valley forms a wide extent of low-lying country. It is,
therefore, interesting to ascertain from which the latter
received its population, or whether it contains so large a number
of endemic species as would warrant the conclusion that it is
itself an independent province. To assist in deciding such
questions as these, we must compare closely the species found in
the district with those of the other contiguous regions, and
endeavour to ascertain whether they are identical, or only
slightly modified, or whether they are highly peculiar.

"Von Martius when he visited this part of Brazil forty years ago,
coming from the south, was much struck with the dissimilarity of
the animal and vegetable productions to those of other parts of
Brazil. In fact the Fauna of Para, and the lower part of the
Amazons has no close relationship with that of Brazil proper; but
it has a very great affinity with that of the coast region of
Guiana, from Cayenne to Demerara. If we may judge from the
results afforded by the study of certain families of insects, no
peculiar Brazilian forms are found in the Para district; whilst
more than one-half of the total number are essentially Guiana
species, being found nowhere else but in Guiana and Amazonia.
Many of them, however, are modified from the Guiana type, and