The Musk Ox (_Ovibos moschatus_), a long-haired ruminant, resembling
what you would suppose a cross between a bull and a sheep might
be,--formerly an inhabitant of Britain with the Elephant and the Hyena,
but now found only on the polar margins of North America,--is becoming
very scarce; and it is probable that before long its last representative
will leave its bones with those of the lamented Franklin and his
companions.

From the more perishable character of vegetable tissues we have far less
data for determining the extinction of plant species; but analogy
renders it highly probable that these also have died out, and are dying
in a corresponding ratio with animals. I am not aware that a single
example can be adduced of a plant that has certainly ceased to exist
during the historic era. But Humboldt mentions a very remarkable tree in
Mexico, of which it is believed only a single specimen remains in a
state of nature. It is the Hand-tree (_Cheirostemon platanoides_), a
sterculaceous plant with large plane-like leaves, and with the anthers
connected together in such a manner as to resemble a hand or claw rising
from the beautiful purplish-red blossoms. "There is in all the Mexican
free States only one individual remaining, one single primeval stem of
this wonderful genus. It is supposed not to be indigenous, but to have
been planted by a king of Toluca about five hundred years ago. I found
that the spot where the Arbol de las Manitas stands is 8825 feet above
the level of the sea. Why is there only one tree of the kind? Whence did
the kings of Toluca obtain the young tree, or the seed? It is equally
enigmatical that Montezuma should not have possessed one of these trees
in his botanical gardens of Huaxtepec, Chapoltepec, and Iztapalapan,
which were used as late as by Philip the Second's physician, Hernandez,
and of which gardens traces still remain; and it appears no less
striking that the Hand-tree should not have found a place among the
drawings of subjects connected with Natural History, which Nezahual
Coyotl, king of Tezcuco, caused to be made half a century before the
arrival of the Spaniards."

There is an example of this interesting plant growing in one of the
conservatories at Kew, but I do not know whence it was obtained. It has
been asserted that it grows wild in the forests of Guatemala.

Leaving plants out of consideration from lack of adequate data, we find
that a considerable number of species of anim