oam.[129]

The mammoth also appears to have existed in England when the temperature
of our latitudes could not have been very different from that which now
prevails; for remains of this animal have been found at North Cliff, in
the county of York, in a lacustrine formation, in which all the land and
freshwater shells, thirteen in number, can be identified with species
and varieties now existing in that county. Bones of the bison, also, an
animal now inhabiting a cold or temperate climate, have been found in
the same place. That these quadrupeds, and the indigenous species of
testacea associated with them, were all contemporary inhabitants of
Yorkshire, has been established by unequivocal proof. The Rev. W. V.
Vernon Harcourt caused a pit to be sunk to the depth of twenty-two feet
through undisturbed strata, in which the remains of the mammoth were
found imbedded, together with the shells, in a deposit which had
evidently resulted from tranquil waters.[130]

In the valley of the Thames, as at Ilford and Grays, in Essex, bones of
the elephant and rhinoceros occur in strata abounding in freshwater
shells of the genera Unio, Cyclas, Paludina, Valvata, Ancylus, and
others. These fossil shells belong for the most part to species now
living in the same district, yet some few of them are extinct, as, for
example, a species of Cyrena, a genus no longer inhabiting Europe, and
now entirely restricted to warmer latitudes.

When reasoning on such phenomena, the reader must always bear in mind
that the fossil individuals belonged to _species_ of elephant,
rhinoceros, hippopotamus, bear, tiger, and hyaena, distinct from those
which now dwell within or near the tropics. Dr. Fleming, in a discussion
on this subject, has well remarked that a near resemblance in form and
osteological structure is not always followed, in the existing creation,
by a similarity of geographical distribution; and we must therefore be
on our guard against deciding too confidently, from mere analogy of
anatomical structure, respecting the habits and physiological
peculiarities of _species_ now no more. "The zebra delights to roam over
the tropical plains, while the horse can maintain its existence
throughout an Iceland winter. The buffalo, like the zebra, prefers a
high temperature, and cannot thrive even where the common ox prospers.
The musk-ox, on the other hand, though nearly resembling the buffalo,
prefers the stinted herbage of the arctic regions, and is