4 
end of the lower mandibles ; and its disproportionate breadth is plainly indicative of the importance of the 
organ to the young animal, both in receiving’ and swallowing’ its food ; the thin fold of integument also, 
which surrounds the base of the mandibles, and extends the angle of the mouth from the base of the lower 
jaw to equal the breadth of the base of the upper one, must increase the facility for receiving the milk 
ejected from the mammary areola of the mother.” “While sucking,” says M. Verreaux, “the young 
continually rub or triturate the mother’s belly with the fore feet, and occasionally with the hinder ones. 
At the end of fifteen to twenty days the new born are covered with a silky hair, and are able to swim.” 
M. Verreaux also describes another mode by which the young obtain the lacteal fluid : “Having a 
considerable number of adults and young at my disposition, I saw the latter accompany their mothers, with 
which they played, especially when they were too far from the bank to take their nourishment. I observed 
that when they wished to procure it, they profited by the moment when the mother was amongst the 
aquatic plants near the land, where there is no current. The female having her back exposed, by the 
exercise of a strong pressure the milk floats to a little distance, and the young may suck it up with 
facility ; and thus they do, turning about so as to lose as little as possible. I cannot, perhaps, better compare 
the appearance of the greasy milk, under these circumstances, than to the iridescent colours produced by 
the solar rays upon stagnant water. 1 have witnessed this fact repeatedly, both daily and nightly. I have 
also remarked that the young, when fatigued, climbed upon the back of the mother, who brought it to land, 
where it caressed her. 
“ The body of this singular animal is covered with a fine, long and thick hair, underneath which is a finer, 
short, very soft fur, resembling the two distinct kinds of fur found in the Seal and Otter ; on the abdomen, 
breast and throat, the fur and hair are of a much finer quality and of a more silky nature than on the 
other parts of the body ; while on the upper surface of the tail the hair is longer and coarser. The general 
colour of the upper surface is a light black ; the under short fur is greyish ; the whole of the under 
surface is ferruginous ; immediately below the inner angle of the eye is a small spot of a light or pale 
yellow ; the legs are short, pentadactyle and webbed ; on the fore feet (which seem to have the greatest 
muscular power, and are in principal use for burrowing and swimming) the webs extend a short distance 
beyond the claws, are loose, and fall back when the animal burrows ; the claws are strong, blunt, and 
well adapted for burrowing ; the hind feet are short, narrow, turned backwards, and when the animal 
is at rest, have, like those of the Seal, some resemblance to a fin ; their action is backwards and 
outwards ; the nails are all curved backwards, and are longer and sharper than those of the fore feet ; 
the web does not extend further than the base of the claws. The head is rather flat, from which project 
two flat lips or mandibles, resembling the beak of a Shoveller Duck, the lower of which is shorter and 
narrower than the upper, and has its internal edges channeled with numerous stria, resembling in some 
degree those seen in the bill of a Duck. The colour of the superior mandible is of a dull dirty greyish- 
black, covered with innumerable minute dots ; the under part of the upper mandible is of a pale pink or 
flesh-colour, as is the internal or upper surface of the lower mandible, the under surface of which is either 
perfectly white or mottled, — in young specimens usually the former, in old ones the latter ; at the base of 
both mandibles is a transverse loose fold or flap of integument, always similar in colour to the skin 
covering the mandibles, that is, dull greyish-black above, and white or mottled below. In the upper 
mandible this is continued to the eyes, and may perhaps afford protection to those organs when the animal 
is burrowing or seeking food in the mud ; the upper fold or flap is continuous with another portion arising 
from the lower mandible also at its base ; the eyes are very small, but brilliant, and of a light brown. 
“ In young specimens, the under surface of the tail, as well as the hind and fore legs near the feet, are 
covered by fine hair of a beautiful silvery-white appearance ; this is lost, however, in the adult, in which 
the under surface of the tail is almost entirely destitute of hair. Whether this proceeds from its trailing 
along the ground, I know not ; but the prevailing opinion among the colonists, for which, however, I could 
not discover any foundation, is that it is occasioned by the animal using the tail as a trowel in the 
construction of its dwelling. 
“The only external difference in the sexes is the presence in the male of a spur, situated on the internal 
part of the leg, some distance above the claws ; this spur, which is moveable and turned backwards and 
inwards, was considered to be poisonous, but some experiments ” (instituted by Mr. Bennett) “ prove that it 
is innocuous : it is entirely wanting in the females. 
“ The size of the Ornithorhynchus varies, but the males are usually found to be slightly larger than the 
opposite sex; the average length is from 18 to 20 inches.” 
In conclusion, I must not omit to call attention to the very valuable details respecting the anatomy of 
this animal, given by Professor Owen and Mr. Bennett, in the “ Transactions of the Zoological Society ” 
above referred to. There will also be found in the “Revue Zoologique” for 1848 some very interesting 
particulars respecting the reproduction and other points in the economy of this animal, by M. Jules 
Verreaux, acquired by personal observation in Van Diemen’s Land. Professor Owen’s remarks on M. 
Verreaux’s observations, published in the “Annals and Magazine of Natural History” for 1848, may also be 
consulted with advantage. 
The Plate represents the two sexes about three-fourths of the natural size. 
