The morning news. [volume] (Savannah, Ga.) 1887-1900, 1898-06-06

existed as land for an incalculable period
but also as desert. Hence we can readily
understand why the animals of Algeria
and the rest of Northern Africa differ for
The most part from those OF that portion
OF the continent lying to the south of the
northern tfopic the Sahara having for
ages acted as an impossible barrier to
most, if not all. But If other evidence were
requisite, there is another reason which
would alone suffice 70 compel US TO re-
gard deserts as areas of great antiquity
The habitable parts of the deserts-and
1t is difficult for the inexperienced to real
lie what barren tracts will suffice for the
maintenance of animal Hfe-are the dwell
ing places of many animals whose color
has become modified to the. needs Of their
environment. And il is quite obvious
that such notifications of color, especial
y when they occur in animals belonging
10 many widely sundered groups, cannot
have taken place suddenly, but must have
been due TO very gradual changes as the
particular species adapted Itself more and
more completely to a desert existence.
Although some of the birds retain the
black wiug-quills of their allies, in all
these creatures the general tone of colora-
ton is extremely pale; browns fawns, rus
sees olives, grays. with more. or less of
black and pink, being the predominant
tones; and how admirably these harmon
glance at the case in the museum is suffi-
clent to demonstrate. Very significant
among these are the desert finches (Eryth-
rospiza), which belong to the brightly-col-
ored group of rose finches; one of these
specially modified species ranging from the
Canaries through the Sahara and Egypt
TO the Punjab, while the, second is an in
habitant of the Monaghan desert. Among
larger animals a considerable number of
the gazeiles are desert jewellers. these in
Guiding the palest-cOlored members of the
group; and lions are likewise to a great
extent inhabitants of deserts--as, indeed, is
true of tawny and pale-colored animals in
general. All the animals above mention
ed belong, however, to widely spread
groups, which are common to the desert
tracts of both Africa and Asia, ana they
do not, therefore, serve to prove the an
tiqulty of any particular desert, as they
or their ancestors might have migrated,
and probably did migrate, from one des-
ert to another. Birds of such groups are,
of course, even more Enthusiastically than
mammals, owing TO their power of flight.
Some degree of caution is necessary in
drawing conclusions that all Isolated des-
ert animals have been evolved in the pre-
else districts they now inhabit. A case i'll
point is afforded by the saga, a pale-col-
ored antelope without any very near kin
dred, inhdbiting the steppes of Eastern
Russia and certain parts OF Siberia, where
1t is accompanied by the hopping Kirghiz
jerboe (Alactaga). Now, since fossilized
remains of both these very peculiar ami
mails have been discovered in the superfc-
ial deposits of the southeastern countries
of England it is a fair inference that ply
steal conditions similar 10 those of the
steppes (Which by the way, are by no
means true deserts) obtained in that part
of our own country a an earlier epoch of
it's history. From their compare lively iso-
lated position in the geological system, as
we'll as from their occurrence in the strata
referred to, both these desert animals eVi-
IDENTIFY indicate very ancient types; ana
they accordingly serve to show not only
thai the semi-desert steppe area formerly
had a much greater western extension
than at present, but probably also that the
existing portion Of that area dates from a
very remote epoch.
In the Arizona desert of North America
il seems to be the case that it's fauna is
largely composed of animals much more
nearly related to those inhabiting the prai-
RE or forest lands of the adjacent districts.
of which. in many cases at any rate, they
constitute mere local races distinguished
by their paler and more sandy type of col
Grafton This is well exemplifed by the
mule deer, which in the Rocky mountalns
is a comparatively dark and richly color
ed animal, but becomes markedly 1oaler on
ing again a more rich coloration hen it
reaches the humid extremity of the Cali
fornian peninusla. Most of the North
American mammals, indeed, acquire SINH
lar pale tints as they reach the Arizona
desert tract; and a practised naturalist
can pick out with comparative ease the
specimens coming from this area from
those of the mOister districts Whether OF
no h. be true in this particular case it may
be laid down as a general rule that the
grea ter the amount of sand TO be found in
a desert, and the greater the difference be-
tween the animals inhabiting that de sert
from those dwelling in the adjacent dis
tricts, the greater will be the antiquity
of the desert itself In the case of a des-
ert forming a complete barrier across a
continent, like the Sahara if the animal is
on one side are quite different from those
on the other, its antiquity win be conclu
sively demOnstrated If, on the other hand,
they are more alike, the age of the desert
VIII be proportionately less.