AUSTRALIAN CAVE-BRECCIAS. 
159 
Sidney, on the river Bell, one of the principal sources of the 
Macquarie, and on the Macquarie itself. The caverns often 
branch off in different directions through the rock, widening 
and contracting their dimensions, and the roofs and floors 
are covered with stalactite. The bones are often broken, but 
do not seem to be water-worn. In some places they lie imbed¬ 
ded in loose earth, but they are usually included in a breccia. 
The remains belong to marsupial animals. Among the 
most abundant are those of the kangaroo, of which there are 
four species, while others belong to the genera Phascolomys^ 
the wombat; Dasyurus^ the ursine opossum; Phalangista^ 
the vulpine opossum; and Hypsiprymnus^ the kangaroo-rat. 
In the fossils above enumerated, several species are larger 
than the largest living ones of the same genera now known 
in Australia. The preceding figure of the right side of a 
lower jaw of a kangaroo {Maeropus atlas^ Owen) wdll at once 
be seen to exceed in magnitude the corresponding part of 
the largest living kangaroo, which is represented in Fig. 92. 
Fig. 92. 
Lower jaw of largest liviug species of kaugaroo. {Maeropus major.) 
In both these specimens part of the substance of the jaw has 
been broken open, so as to show the permanent false molar 
(a. Fig. 91), concealed in the socket. From the fact of this 
molar not having been cut, we learn that the individual was 
young, and had not shed its first teeth. 
The reader will observe that all these extinct quadrupeds 
of Australia belong to the marsupial family, or, in other 
words, that they are referable to the same peculiar type of 
organization which now distinguishes the Australian mam¬ 
malia from those of other parts of the globe. This fact is 
one of many pointing to a general law deducible from the 
fossil vertebrate and invertebrate animals of times imme¬ 
diately antecedent to our own, namely, that the present geo¬ 
graphical distribution of organic forms dates back to a peri¬ 
od anterior to the origin of existing species; in other words. 
