and another closely allied species rare in the same district --
why should we feel such great astonishment at the rarity being
carried one step further to extinction? An action going on,
on every side of us, and yet barely appreciable, might surely
be carried a little further, without exciting our observation.
Who would feel any great surprise at hearing that the Magalonyx
was formerly rare compared with the Megatherium, or that one of
the fossil monkeys was few in number compared with one of the
now living monkeys? and yet in this comparative rarity, we
should have the plainest evidence of less favourable conditions
for their existence. To admit that species generally become
rare before they become extinct -- to feel no surprise at the
comparative rarity of one species with another, and yet to
call in some extraordinary agent and to marvel greatly when
a species ceases to exist, appears to me much the same as
to admit that sickness in the individual is the prelude to
death -- to feel no surprise at sickness -- but when the
sick man dies to wonder, and to believe that he died through
violence.

[1] Mr. Waterhouse has drawn up a detailed description of this
head, which I hope he will publish in some Journal.

[2] A nearly similar abnormal, but I do not know whether
hereditary, structure has been observed in the carp, and
likewise in the crocodile of the Ganges: Histoire des Anomalies,
par M. Isid. Geoffroy St. Hilaire, tom. i. p. 244.

[3] M. A. d'Orbigny has given nearly a similar account of these
dogs, tom. i. p. 175.