MARSUPIALIA. 73 



ORDER IV. 



MARSUPIALIA. 



So many are the singularities in the economy of the Marsupialia or pouched 

 animals, as they are termed, which we formerly placed at the end of the 

 Carnaria as a fourth family of that great order, that it appears to us they 

 should form a separate 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 production of their young, whose 

 state of development at birth is extremely 

 small. Incapable of motion, and hardly ex- 

 hibiting the germs of limbs and other ex- 

 ternal organs, these diminutive beings attach 

 themselves to the mammae of the mother, 

 and remain fixed there until they have acquired a degree of development 

 similar to that in which other animals are born. The skin of the abdomen is 

 almost always so arranged about the mammae as to form a pouch in which 

 these imperfect little 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 mus- 

 cles of the abdomen, support the pouch. These bones are also found in the 

 male, and even in those species in which the fold that forms the pouch is 

 scarcely visible. 



Another peculiarity of the Marsupialia is, that notwithstanding a general 

 resemblance of the species to each other, so striking that for a long time they 

 were considered as one genus, they differ so much in the teeth, the organs of 

 digestion, and the feet, that if we rigorously adhered to these characters, we 

 should be compelled to separate them into several orders. They carry us by 

 insensible gradations from the Carnaria to the t Rodentia, and there are even 

 some animals which have the pelvis furnished with similar bones ; but which, 

 from the want of incisors or of all kinds of teeth, have been approximated to 

 the Edentata, where, in fact, we shall leave them, under the name of Mono- 

 tremata. 



The first subdivision of the Marsupialia is marked by long canini, and small 

 incisors in both jaws, back molars bristled with points, and all the characters 

 in general of the insectivorous Carnaria ; the animals that compose it are also 

 perfectly similar to the latter in their regimen. 



DIDELPHIS, LinncEiis. 



The Opossums, which of all the Marsupialia have been the longest known, form 

 a genus peculiar to America. They have ten incisors above, the middle ones 



