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and shallower than in the present fossil, and is not only placed anterior 

 to the astragalar surface, but is continuous with it. Not to dwell on 

 the differences which the comparative anatomist must have immediately 

 perceived from the description of the present most remarkable, bone 

 in the corresponding one of the Ruminantia, the Quadrumana, the Car- 

 nivora and Rodentia, I proceed at once to state that it is only in the 

 equipedal Marsupialia, and more especially in the Koala and Wombat, 

 that we find the articular surfaces of the calcaneum two in number and 

 of the same general form, proportions and relative position as in the 

 fossil under consideration : the nearly flat internal and superior astragalar 

 surface is, however, proportionally narrower in the Wombat ; its outer 

 depressed angle is shallower ; the calcaneal projection is directed down- 

 wards and inwards ; the strong peroneal tendon indents the outer side 

 of the calcaneum with a groove but does not perforate the bone. The 

 calcaneum of the Kangaroo has a totally different form from the fossil ; in 

 the leaping Marsupialia the heel is subcompressed and much elongated ; 

 the astragalar surface is divided into two small distinct parts ; the cu- 

 boidal facet is anterior, and convex vertically, &c. In conclusion, it may 

 be stated that the large fossil calcaneum here described combines the 

 essential characters of that of the Wombat, with some features of that 

 of the Mylodon and Mastodon, and others which are peculiar to itself: 

 the single broad astragalar surface, with its external depressed portion, 

 coincides with the characters of the large fossil astragalus No. 1509, 

 though the different form of the astragalar surface appears to show the 

 present calcaneum to belong to a distinct species of marsupial Pachy- 

 derm. 



That a large quadruped, whose nature andaffinities that term expresses, 

 formerly inhabited Australia, the characters of the present os calcis would 

 alone have rendered highly probable : and since the same conclusions are 

 deducible from the portions of jaw Nos. 1460 and 1461, which corre- 

 spond in size, mineralized condition, locality and stratum with the pre- 

 sent calcaneum, it is highly probable that they all belong to the Dipro- 

 todon australis, a species whose affinities to the Wombat were perceived 

 by the characters of the single tusk and fragment of jaw transmitted by 



