ORDER II. 
MARSUPIATA. 
Implacental mammals, the young of which are brought forth prematurely, and received, in most instances, into a peculiar 
pouch, situated on the lower part of the abdomen of the female; both sexes are furnished with two bones, called marsupial 
bones, which are attached to the anterior margin of the pelvis. The brain is deficient, both in the corpus callosum and septum 
lucidum ; the cerebrum is small, in comparison with the size of the animal, contracted in front; its surface is smooth, or presents 
but few convolutions; the cerebellum is entirely exposed, and has the vermiform process large in proportion to the lateral lobes; 
the olfactory lobes large. Two vents eavoe enter the heart. 1 
In the preceding diagnosis are embraced the chief characteristics of a very remarkable order 
of mammals, of which the opossum and kangaroo are familiar examples. They are most 
characteristic of Australia at the present day; one group is found in America, one genus, with 
two species, belonging to the United States. Certain species exist in the Moluccas, as well as in 
New Guinea. 
The Marsupiata present a great variety of forms, agreeing in the characters presented above, 
hut of totally different external appearance, and representing nearly all the other orders of 
mammals. Indeed, some naturalists assign them respectively to the different groups they most 
resemble, while others, again, give to them the position of a distinct class of implacentalia, as 
distinguished from the placental mammals. Thus, the Quadrumana are represented by the Pha- 
langers, the Carnivora by the Dasyuri, the Insectivora by the small Phascogales, the Ruminantia 
by the Kangaroos, and the Edentata by the Monotremes. The Cheiroptera are not represented 
by any known Marsupalia, and the Rodents by a single species only. 
The most striking peculiarity of the Marsupiata, in addition to the pouch, consists in the 
premature birth of the young, and consequent imperfect state of development which they present 
at this period. The young of the great kangaroo, {Macropus major,) twelve hours after birth, 
resembled an earth worm in the color and semi-transparency of its integument; its whole 
length, from nose to end of tail, did not exceed an inch and two lines. 
In addition to the other differences between the placental and non-placental mammals, there 
are striking peculiarities to he found in the character of the teeth. While in the former the 
normal number of incisors in each jaw is six, in the latter they vary from ten above and eight 
below, to eight above and six below, or six above and two below. All Marsupialia, with very 
few exceptions, have four true molars. 
Waterhouse considers the Monotremata , embracing the Echidna and Ornithorynchus, as one 
section of the Marsupiata, the more typical ones being divided by him into Macropodidae, 
Peramelidae , Phascolomyidae , Phalangistidae, Didelphidae , and Dasyuridae. It is with the 
Didelphidae only that we have here to do. 
1 Waterhouse, Natural History of the Mammalia, vol. 1, 1846, page 1, from which the general remarks in this article are 
chiefly deriv 
