THE PECULIAR 'POSSUM 97 



of the 'possum, show that it is a very primitive 

 mammal, one of the very oldest mammals, so close 

 /to the beginning of the mammalian line that there 

 are only two other living " animals " (we can hardly 



call them mammals) older and more primitive the 



i porcupine ant-eater, and, oldest of all, the duck-bill, 



2 not " older " at all perhaps, but only more primitive. 



For the duck-bill, though classed as a mammal, 



f not only has the bill of the duck, but also lays eggs 



; like the birds. The porcupine ant-eater likewise 



', lays eggs, and so seems almost as much bird or rep- 



/ tile as mammal. And as the birds and reptiles lived 



\ upon the earth before the age of mammals, and are 



;/ a lower and more primitive order of creatures, so 



"' the duck-bill, the porcupine ant-eater, and the 'pos- 



\* sum, because in their anatomy they are like the birds 



