~ 122 MAMMALIA. 
Voy. Ill. (The Sea-Cow.) It inhabits the Arctic seas, sur- 
. — passes the largest Ox in size, attains the length of twenty feet, 
and is covered with a short yellowish hair. It is sought for on 
account of its oil and,tusks; the ivory of which, although 
rough grained, is employed in the arts. The skin makes ex- 
cellent coach braces.(1) 
ORDER IV. 
MARSUPIALIA. 
So many are the singularities in the economy of the Marsu- 
pialia or pouched animals, as they are termed, which we for- 
merly placed at the end of the Carnaria as a fourth family of 
that great order, that it appears to us they should form a se- 
parate and distinct one, particularly as we observe in them a 
kind of representation of three very different orders. . 
The first of all their peculiarities is the premature produc- 
tion of their young, whose state of development at birth is 
scarcely comparable to that of an ordinary foetus a few days 
after conception. Incapable of motion, and hardly exhibiting 
the germs of limbs and other external organs, these diminutive 
beings attach themselves to the mamme of the mother, and 
remain fixed there until they have acquired a degree of de- 
velopment similar to that in which other animals are born. 
‘The skin of the abdomen is almost always so arranged about 
the mamme as to form a pouch in which these imperfect lit- 
tle animals are preserved as in a second uterus; and to which, 
long* after they can walk, they always fly for shelter at the 
approach of danger. Two particular bones attached to the 
pubis, and interposed between the muscles of the abdomen, 
support the pouch. ‘These bones are also found in the male, 
and even in those species in which we fold that forms the 
pouch is scarcely visible. 
(1) Previous to my arrangement, the Lamantins and Dugongs, much more 
nearly allied to the Cetacea, were very improperly united with the Morses. 
