SUB-CLASS II. MARSUPTIALIA.
(Pouched Animals.)
Most zoologists are now agreed that the animals we are about to consider, constitute a group, which, however limited in extent, is shewn by the importance of the characters. by which it is distinguished to be equal in rank, not to an Order of Mammalia, but to all the other Mammalia combined. The most striking of these are the immature condition of the young at the time of birth, and its reception into a pouch (marsupium) or fold of the skin on the abdomen of the female, in which it is protected from exposure to the air and injury, while, suspended from the teat, to which it is very early attached, it gradually assumes the form of its adult condition, and acquires the powers necessary for its independent existence. For some time, however, after it is able to procure its own living, and to run and play by the side of its mother, the young marsupial instinctively flees to the maternal pouch for protection on the approach of danger.
But these are far from being the only characters in which the Marsupiatia differ materially from the Placentalia. Important peculiarities in the reproductive organs, in the arterial system, and in the structure of the brain; the open condition of the skull, the bones of which remain per-
