THE DUCK-BILLS. 239 
would remain quiet, huddled up with the young ones, but at 
night would become very restless, and eager to escape from her 
place of confinement. A general growl would issue forth from 
the group if disturbed when asleep.” 
As indicated in the foregoing extract, the fur of aged indi- 
viduals becomes frequently very rough and ragged, so that the 
whole animal presents a dishevelled and almost disreputable 
appearance, in striking contrast to the sleekness and beauty of 
the coat of the young before they have left the burrow. Re- 
garding the difference in these respects, between the old and 
the young Duck-bills, the author above quoted observes that 
“in the young animals the upper beak was of a similar colour 
to the same organ in the old specimens; but on its under sur- 
face the colour was a beautiful pink, in consequence of the 
minute blood-vessels being distinctly visible through the deli- 
cate epidermis, like the bloom of rosy health on the cheek of 
an infant. The legs close to the feet were fringed with fine 
silvery hairs, and the fur on the back, although of a more 
delicate nature, was similar in colour to that of older speci- 
mens; yet the ferruginous hue of the whole extent of the 
under part of the chest and abdomen had a lighter tinge, 
dependent probably on the age of the animal.” 
It may be mentioned in this connection that it has often 
been considered that there are several species of Duck-bill, but 
it appears that such supposed species have been founded upon 
different individual variations of Ovrnithorhynchus anatinus, 
due to differences of age and peculiarities of coloration. 
Writing many years ago on this subject, Waterhouse observed 
that “‘in the large and mature specimens the fur is crisp and 
of a dull brown colour ; whilst in the smaller specimens it is of 
a bright brown hue, and soft to the touch, and, on the under- 
parts of the body, is almost white. Those of smaller size and 
brighter colouring have received the specific names rufus, 
