The platypus is aquatic in its habits, passing most of its time in the water or close to the margin of lakes and streams, swimming and diving with the greatest ease, and forming for the purpose of sleeping and breeding deep burrows in the banks, which generally have two orifices, one just above the water level, concealed among long grass and leaves, and the other below the surface.
6pves, 6pveOos, bird, and pveyxos, bill) is therefore now universally adopted as the scientific designation, although duck-billed platypus (Gr.
Australia and Tasmania possess two animals of this order - the echidna, or spiny ant-eater (hairy in Tasmania), and the Platypus anatinus, the duckbilled water mole, otherwise named the Ornithorhynchus paradoxus.
The anatomical differences by which the platypus, and its only allies the echidnas, are separated from all other mammals, so as to form a distinct sub-class, are described in the article Monotremata, where also will be found the main distinctive characters of the two existing representatives of the group. It is there stated that the early stages of the development of the young are not yet fully known.
Poulton, showed that the ovum of the platypus was large compared with that of other mammals, whilst W.
Caldwell showed that it was filled with yolk, and finally established the fact that Platypus as well as Echidna is oviparous.
Adult monotremes are in like case, although the duckbilled platypus (Ornithorhynchus) has teeth when young on the sides of the jaws.