Orper MARSUPIALIA. 
MARSUPIALS. 
The Marsupials, or so-called Pouched Mammals, comprise a large 
number of curious animals, including the Kangaroos, Wombats, etc., and 
are mostly confined to the Australian region. They are represented, 
however, in the new world by the Opossums (Didelphiide), a number of 
species of which are found in North and South America; and also in the 
latter country by Caenolestes,* a representative of the, until lately, 
supposed extinct family Epanorthide. 
As the name marsupial implies, in many cases the female is furnished 
with an external abdominal pouch in which the young, which are born in 
a very incomplete stage of development,t are placed by the mother 
and suckled until they are sufficiently grown to be able to move about by 
themselves. In Phascologale, however, the pouch is only present in 
rudiment, and it is apparently entirely absent in Myrmecobius. In the 
American members of the order the pouch is often absent, sometimes 
rudimentary, and occasionally well developed 
Some Marsupials are herbivorous, others insectivorous, and a few are 
carnivorous. The North American Opossums seem to be practically 
omnivorous. Members of the family are terrestrial, arboreal or bur- 
rowing, and one (Chironectes), a small Central and South American 
species, has webbed hind feet and is semiaquatic. 
Among members of this order usually only one tooth of the milk set 
is functional, the fourth premolar; a developed clavicle is always present. 
There are differences in brain characters which distinguish Marsupials 
from higher mammals, among which is the almost total absence of a true 
corpus callosum. ‘The cloaca is reduced and shallow. A true allantoic 
placenta is rarely present (so far as known, only in Parameles). The 
uterus and vagina are double. The mamme vary in number but are 
* A number of specimens of this little known Marsupial were taken by Mr. W. H. 
Osgood in the mountains of western Venezuela and eastern Colombia in the spring of 
1911. Study of this material is now under way and will be the subject of a special 
paper which will appear later in the Publications of this Museum. 
{ Flower and Lydekker say, ‘‘In this stage of their existence they are fed by 
milk injected into their stomach by the contraction of the muscles covering the 
mammary gland, the respiratory organs being modified temporarily, much as they 
are permanently in the Cetacea, the elongated upper part of the larynx projecting 
into the posterior nares, and so maintaining a free communication between the lungs 
and the external surface independently of the mouth and gullet, thus averting the 
danger of suffocation while the milk is passing down the latter passage.” (Mammals 
Living and Extinct, 1891, pp. 130-131.) 
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