Page:Geology and Mineralogy considered with reference to Natural Theology, 1837, volume 1.djvu/68

 64 of general occupation by warm-blooded terrestrial Mammalia.

The only terrestrial Mammalia yet discovered in any secondary stratum, are the small marsupial quadrupeds allied to the Opossum, which occur in the oolite formation, at Stonesfield, near Oxford. The jaws of two species of this genus are represented in Plate 2. ; the double roots of the molar teeth at once refer these jaws to the class of Mammalia, and the form of their crowns places them in the order of Marsupial animals. Two other small species have been discovered by Cuvier, in the tertiary formations of the basin of Paris, in the gypsum of Mont Martre.

The Marsupial Order comprehends a large number of existing genera, both herbivorous and carnivorous, which are now peculiar to North and South America, and to New Holland, with the adjacent islands. The kangaroo and opossum are its most familiar examples. The name of Marsupialia is derived from the presence of a large external marsupium, or pouch, fixed on the abdomen, in which the fœtus is placed after a very short period of uterine gestation, and remains suspended to the nipple by its mouth, until sufficiently matured to come forth to the external air. The discovery of animals of this kind, both in the secondary and tertiary formations, shows that the Marsupial Order, so far from being of more recent introduction than other orders of mammalia, is in reality the first and most ancient condition, under which animals of this class appeared upon our planet: as far as we know, it was their only form during the secondary period; it was co-exist ant with many other orders in the early parts of the tertiary period; and its geographical distribution in the present creation, is limit; ed to the regions we have above enumerated.