98 
which projects beyond the extremities of the toes, is loose, and can, therefore, fall 
back when the animal burrows. Owing to this arrangement* the Ornithorhyn¬ 
chus has the full benefit of its broad foot as a paddle when swimming ; and when 
making its way into the earth, where strength more than breadth is requisite, the 
falling back of the w r eb increases the power of resistance in the foot, and, at the 
same time, allows the strong blunt claws to come into operation. The male has a 
moveable spur upon the posterior and inner surface of the hind leg, a little dis¬ 
tance above the claws. 
The head, like the body, is compressed horizontally ; the eyes of a light brown 
colour, very small, but brilliant, are placed rather backwards. There is no pro¬ 
jecting external ear, but the orifice of the auditory canal is situated behind and 
external to the eye, and the animal has the power of opening and closing it at 
pleasure. The mouth or beak is the most characteristic part of this curious quad¬ 
ruped ; it is formed of two flat projecting lips or mandibles, of a cartilaginous 
structure, and slightly serrated at the sides ; altogether bearing a very strong re¬ 
semblance to the beak of the Shoveller Duck. It is of a dirty greyish black 
colour, and covered with innumerable minute dots. At the base of each mandible 
is a loose projecting fold of skin, of the same dark colour as the beak, and to this 
different uses have been assigned. Mr. Bennett is of opinion that it affords pro¬ 
tection to the eyes when the animal is engaged in burrowing or seeking its food 
in the mud; Sir Everard Home* considers the use of these folds to be, to prevent 
the beak from being pushed into the soft mud beyond this part, which is so broad 
as completely to stop its further progress. 
The possession of cheek-pouches is the only other structural peculiarity to 
which it is necessary to refer in the description of this animal. When recently 
captured, they generally contain mud and small stones mixed up with the animal- 
culse on which the creature feeds ; and it is supposed that in these pouches the 
food undergoes trituration and other changes, preliminary to its digestion in the 
stomach. 
The Ornithorhynchus is ovoviviparous, but suckles its young, after birth, like 
most other quadrupeds. 
From the singular organization of this creature, we can scarcely wonder at the 
indicision of naturalists, in the first instance, as to what place it ought to occupy 
in the animal series. To increase the dilemma, it was always believed, till very 
recently, that the Ornithorhynchus propagated its species by means of eggs, but 
the investigations of Mr. Bennett and Mr. Owenf have completely set that ques¬ 
tion at rest. In its mode of generation, it resembles the reptile tribe; its want 
of bony teeth, the singular formation of its duck-like bill, and the possession of 
* Philosophical Transactions for 1800. 
t Philosophical Transactions, for 1834; and Zoological Transactions, vol. i., p. 221. 
