re to the myrmecobius and allied marsupials of
Australia. The other contemporary genus, called phascolotherium, agrees
much more nearly in osteological character and precisely in the number
of the teeth with the opossums; and is believed to have been truly
marsupial. (Fig. 10.)

[Illustration: Fig. 10.

_Natural size._

Phascolotherium Bucklandi, _Owen_. (_Syn._ Didelphis Bucklandi, _Brod._)
Lower jaw, from Stonesfield.[220]

1. The jaw magnified twice in length. 2. The second molar tooth
magnified six times.]

The occurrence of these most ancient memorials of the mammiferous type,
in so low a member of the oolitic series, while no other representatives
of the same class (if we except the microlestes) have yet been found in
any other of the inferior or superior secondary strata, is a striking
fact, and should serve as a warning to us against hasty generalizations,
founded solely on negative evidence. So important an exception to a
general rule may be perfectly consistent with the conclusion, that a
small number only of mammalia inhabited European latitudes when our
secondary rocks were formed; but it seems fatal to the theory of
progressive development, or to the notion that the order of precedence
in the creation of animals, considered chronologically, has precisely
coincided with the order in which they would be ranked according to
perfection or complexity of structure.

It was for many years suggested that the marsupial order to which the
fossil animals of Stonesfield were supposed exclusively to belong
constitutes the lowest grade in the class Mammalia, and that this order,
of which the brain is of more simple form, evinces an inferior degree of
intelligence. If, therefore, in the oolitic period the marsupial tribes
were the only warm-blooded quadrupeds which had as yet appeared upon our
planet, the fact, it was said, confirmed the theory which teaches that
the creation of the more simple forms in each division of the animal
kingdom preceded that of the more complex. But on how slender a support,
even if the facts had continued to hold true, did such important
conclusions hang! The Australian continent, so far as it has been
hitherto explored, contains no indigenous quadrupeds save those of the
marsupial order, with the exception of a few small rodents, while some
neighboring islands to the north, and even southern Africa, in the same
latitude as Australia, abound in mammalia of every tribe except the
marsup