in Australia . 
153 
smaller or lower one which runs across the base of the first 
at the anterior part of the crown of the tooth, are here pre¬ 
served. The apex of both the higher ridges lias been worn 
by mastication, but not to such an extent as is usually seen 
in the small deciduous molars of the Mastodons: there is less 
trace of a division of tile summit of the ridge into mammilla; 
than would be presented by a similar-sized molar, equally 
worn down, oi the Mastodon giganteus , in which the two 
mammillae would be indicated by a median constriction. The 
transverse ridges are still more subdivided in the other known 
species, as M. longirostris, M. latidens, M. angustidens, or M. 
dephantoides : the Australian tooth more resembles that of the 
Dinotherium in the simplicity of the transverse eminences, but 
there is a deposit of cement or crusta petrosa at the bottom 
of the intervening valleys, which I have not observed in any 
molar of Dinotherium . As the bones of the extremities of 
this most remarkable genus, the Dinotherium , have not yet 
been discovered, the affinities of the Australiam Pachyderm 
to that genus do not at present derive further elucidation from 
the femur above described. 
The close relationship of the Mastodon to the Dinotherium 
has received additional proof by the discovery of the two tusks 
of the lower jaw in the young individuals of the Mastodon, 
and by the retention of one of these as a sexual distinction of 
the male, m Mastodon giganteus : and the highly interesting 
member of the ancient fauna of Australia, revealed by the 
remains above described, must be referred, on their evidence 
to the same natural family of gigantic Pachyderms as that 
which includes the Mastodons and Dinotkeres, and to a spe¬ 
cies distinct from any yet determined. The interests of science 
will, perhaps, be best consulted by refraining from the im¬ 
position of any generic or specific name until the requisite 
characters are obtained; and of this most desirable acquisition 
reasonable hopes may be entertained, since the zealous and 
distinguished officer to whom we are indebted for all the in¬ 
teresting fossils yet met with in Australia promises a con¬ 
tinuance of his valuable aid. At the conclusion of his letter 
Sir T. L. Mitchell states, “ I am promised part of a rib and 
other bones by the gentleman who gave the tooth, and I have 
some hopes of obtaining a jaw-bone; when I do, it shall be 
sent to you forthwith/' 
The fossils above described will be presented, in the name 
of Sir T. L. Mitchell, to the Museum of the Royal College 
of Surgeons, London. They cannot be contemplated without 
suggesting many interesting reflections. They tell us plainly 
that the time was when Australia's arid plains were trodden 
by tlie hoofs of heavy Pachyderms; but could the land then 
have been, as now, parched by long-continued droughts 
with dry river-courses containing here and there a pond of 
water . All the facts and analogies which throw light on the 
