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but at least there is no doubt that such existed in times of post- 
tertiary date. 
As to our third point — the geological relations of the kan- 
garoo — we may say, then, that “the kangaroo is one of an 
order of animals which ranged over the northern hemisphere 
in triassic and oolitic times , one exceptional family lingering 
in Europe to the Eocene period , and in America to the present 
day . That the kangaroo itself is a form certainly become 
fossil in its own region , where , in times geologically recent , 
creatures allied to it , but of vastly greater bulk, frequented the 
Australian plains .” 
We may now, then, proceed to answer finally the question, 
66 What is a kangaroo f ” We may do so because the meaning 
of the technical terms in which the answer must necessarily be 
expressed (if not of undue length) have been now explained, as 
far as space has allowed. 
We may say, then, that 44 the kangaroo is a didelphous (or 
marsupial) mammal , of the family Macropodid^e ; an inha- 
bitant of the Australian region , and connected, as respects its 
order, with triassic times , and possibly even as regards its 
family also, though certainly (as regards the latter) with the 
time of the post-tertiary geological deposits .” 
We have seen what are didelphous and what are mena- 
delphous mammals; what are the respective values of the 
terms u order,” 64 family,” and 44 genus,” and also in what 
respect the kangaroo differs from the other families of the 
marsupial order. We have also become acquainted with the 
distribution of organic life now and with the inter-relations of 
different geological strata, as far as those phenomena of space 
and of time concern our immediate subject. 
By becoming acquainted with these matters, and by no other 
way, is it possible to give an intelligent answer to the question, 
“ What is a kangaroo f ” 
DESCRIPTION OF PLATE CXXVIII. 
Fig. 1. Macropus Parryi. (From the Transactions of the Zoological 
Society, vol. i. p. 300.) 
„ 2. Sole of Right Foot of Kangaroo. 
„ 3. Cuscus Orientalis. (From the Proceedings of the Zoological Society 
for 1858, Pl. LXI.) 
„ 4. T/iylacinus Cynocephalus. (From the Proceedings of the Zoological 
Society for 1850, PI. XVIII.) 
