THE OPOSSUM MOUSE. 457 
into two folds of skin, so that the mother is obliged to find other means of carrying 
her young from place to place. In the structure of the animal there is an admirable 
provision for sustainmg the pouch and its contents, and preventing it from exerting too 
painful a “drag” upon the skin and walls of the abdomen. Two supplementary bones, 
called, from their position in the pouch, the marsupial bones, issue from the pelvis, and 
are directed forward almost parallel to the spine. On account, however, of the method in 
which certain muscles wind round the marsupial bones, and taking into consideration 
the fact that these structures are found in both sexes, Mr. Owen considers that their chief 
aim is not so much in affording support to the ponch as in compressing the numerous 
glands, so as to aid the feeble young in gaining nourishment. 
We will now leave their general consideration, and proceed t omine some of the 
principal species which are contained in this wonderful group of. an 
At the head of the Macropide are placed a small but interc? f rs 
animals, which are called Phalangistines, on account of the curive m1 
two of the toes belonging to the hinder feet are joined together as far as the ph a wnges 
The feet are all formed with great powers of grasp, and “their structure is intended to fit 
them for procuring their ‘food 
among the branches of the trees, 
on which they pass the ereater 
portion of their existence. 
These creatures fall naturally 
into three subdivisions—namely, 
the Petaurists, er those which are 
furnished with a parachute-like 
expansion of the skin along the 
flanks, much resembling a similar 
structure in the colugo, or flying 
lemur, which has been already de- 
scribed in page 88 ; thePhalancists, 
or those which are devoid of the 
parachute, and are furnished with 
a long prehensile tail; and the 
Koalas, or those which are devoid 
of both parachute and tail. <Ac- 
cording to many excellent autho- 
rities, these three subdivisions are, 
in fact, three genera, which com- 
prise the whole of the Phalangis- OPOSSUM MOUSE. —Aorébates pygmmus 
tines, and which render any further 
separation into genera entirely 
unnecessary, 
First, and least of the Phalangistines, is the beautiful little animal which is called the 
Opossum Mouse in some parts of “the country, and the FLyrvc Mouss in others. 
This pretty little creature is about the size of our common mouse, and when it is 
resting upon a branch, with its parachute, or umbrella of skin, drawn close to the body 
by its own elasticity, it looks very like the common mouse of Europe, and at a little 
distance might easily be taken for that animal. In total length it rather exceeds six 
inches, the length of its head and body being about three inches and a half, and that of 
the tail not quite three inches. On account of its minute size, this animal is also called 
the PicMy PerauRIst. 
In the colour of the upper portions of the body the Opossum Mouse 1s of the well- 
known mouse tint, slightly sprinkled with a reddish hue ; but on the abdomen, and under 
portions of the skin-parachute, the fur is beautifully white. The line of demareation 
between the hair is very well defined, and there is a narrow stripe of darker brown that 
marks out the line of juncture. When the animal is at rest, the parachute closes by its 
