PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
545 
anchylosed lumbar vertebra of the Mylodon ; but the bodies of the dorsal vertebrae in 
the great extinct Bruta are longer and narrower in proportion to their breadth than in 
the present fossil. In the Kangaroo the upper surface of the body of the dorsal and 
lumbar vertebrae is perforated by two vascular canals, which pass down vertically and 
open below by a single or double outlet. In the Wombat the middle of the upper surface 
of the bodies of the dorsal and lumbar vertebrae exhibits a single large and deep depres- 
sion, which in the dorsal vertebrae has no inferior outlet, and in this character they closely 
resemble the present fossil. The dorsal vertebrae of the Wombat are, however, longer in 
proportion to their breadth. 
Thus the present mutilated vertebra alone would support the conclusion that there 
had formerly existed in Australia a mammiferous quadruped, superior to the Ehinoceros 
in bulk, and distinct from any known species of corresponding size. It is interesting 
and instructive to find one well-marked character in it, viz. the median excavation on 
the upper part of the body, repeated in the same vertebrae of one of the largest of the 
existing Marsupialia. 
The remaining evidences of vertebrae in the Boydian or purchased series of Diprotodont 
Fossils in the British Museum consist of five centrums and two pairs of detached ter- 
minal epiphyses of those elements. 
The centrums, in the absence of any costal or haemapophysial depression, in their 
increased length and greater expanse of the neural canal, are referable to the lumbar 
series. Three retain the coalesced bases of the neurapophyses, yet these do not develope 
diapophyses in the extent to which they are preserved. 
The foremost of these lumbar centrums shows a length of 2 inches 4 lines at its lower 
part, increasing to 2 inches 8 lines at its upper part ; the others, with slight general gain 
of size, show the same proportions. Thus the one which seems the last of the series has 
a length of 3 inches 3 lines at the lower part, and of 3 inches 8 lines at the upper part 
of the centrum. Thus we may infer that the part of the spine from which these vertebrae 
have come was habitually bent in JDiprotodon with the concavity downward. The degree 
of increased length in the last over the longest of the other three centrums indicates two 
or three missing vertebrae intervening between those to hand. The Kangaroo has six 
lumbar vertebrae, the Koala eight, the Wombats only four ( Phascolomys vombatus) or 
five ( Phascolomys latifrons). Six lumbars is the rule in Marsupialia , and I incline to 
view Diprotodon as amenable thereto, rather than as repeating the exceptional formula 
of Phascolomys* . 
In the foremost of the five fossil lumbar centrums a small protuberance from the upper 
and fore part of one side indicates the rudiment of a diapophysis ; it is not present on 
* As I was led to note in my * Osteology of Marsupialia,’ he. cit., p. 396, the number of free trunk-vertebra) 
is significantly constant in that order, whatever he the difference of costal formula ; thus, Phascolarctos has 11 
costal, 8 lumbar, =19 ; Petaurus, 12 costal, 7 lumbar, =19 ; Macropus, PTialangista, Perameles, Myrmecobius, 
Phascogale, Diclelphys, Dasyurus, Sarcophilus, Thylacinus, have severally 13 costal, 7 lumbar, =19 ; Phasco- 
lomys vombatus has 15 costal, 4 lumbar =19. 
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