ON THE EXTINCT MAMMALS OF AUSTRALIA. 229 



with such molar teeth in the case of the great Australian Pachydermoid. I 

 proceed, therefore, to notice two of the most complete bones which were dis- 

 covered in the same stratum and locality as the portions of the lower jaw of 

 the Diprotodon from the bed of the Condamine river, and which, from their 

 agreement in size with those mandibular fragments, belong very probably to 

 the same species ; they have undergone precisely the same mineral change. 



The first of these is the body of a dorsal vertebra of unquestionably a 

 mammalian quadruped of the size of the Diprotodon australis. It measures 

 two inches three lines in antero-posterior diameter, three inches in vertical 

 diameter, and four inches nine lines in transverse diameter. Both articular 

 extremities are flat, the epiphysial plates are anchylosed ; but where they are 

 broken away, the radiating rough lines, characteristic of the epiphysial sur- 

 face, indicate that the union was tardy, and had been recently effected before 

 the animal perished. This vertebra differs by its compressed form and the 

 flattening of the articular ends from the dorsal vertebrae of the ordinary pla- 

 cental Pachyderms, but resembles in these characters the dorsal vertebrae of 

 the Proboscidians {Elephas, Mastodoti). In these, however, the breadth of 

 the vertebral body is not so great as in the fossil. From the Cetacean verte- 

 brae the present fossil is distinguished by the large concave articular surface 

 at the upper and anterior part of the side of the body for the reception of 

 part of the head of a rib : this costal surface, which is not quite entire, ap- 

 pears to have been about an inch and a half in diameter. The neurapophyses 

 are anchylosed to the centrum, but the internal margins of their expanded 

 bases are definable, and have been separated by a tract, rather less than an 

 inch in breadth, of the upper surface of the centrum. At the middle of this 

 surface there is a deep transversely oblong depression : a similar depression 

 is present in some of the dorsal vertebrae, and in the anchylosed lumbar ver- 

 tebra of the Mylodon ; but the bodies of the dorsal vertebras, in all the great 

 extinct Bruta, are longer and narrower in proportion to their breadth than in 

 the present fossil. The upper and posterior margin is here indented on each 

 side by the dorsal nerve, which, in the monotrematous Echidna, perforates 

 the base of the neurapophyses ; otherwise the body of the dorsal vertebra in 

 that Implacental corresponds in its proportions, and in the depression on the 

 upper part of the body, with the present fossil. In the Kangaroo the upper 

 surface of the body of the dorsal and lumbar vertebra 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 vertebra exhibits a single large and deep depression, 

 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 Rhinoceros in bulk, 

 and distinct from any known species of corresponding size ; and it is interesting 

 to find one well-marked character in it, viz. the median excavation on the 

 upper part of the body, repeated by one of the larger of the existing Mar- 

 supialia. 



The second fossil speaks more decisively both for the Marsupial nature of 

 the species to which it belonged and as to its more immediate affinities in that 

 Order. It is the right os calcis, which measures six inches in length and five 

 inches and a half in breadth, presents two large articular surfaces at right 

 angles to each other upon its upper and anterior part, has a short calcaneal or 

 posterior process, which is broad, depressed and bent upwards, and a short 

 thick obtuse process directed downwards from the internal and under part of 



