295 



1 462. The body of a dorsal vertebra of a large quadruped, probably the Dipro- 

 todon 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 epiphy- 

 sial plates are anchylosed ; but where they are broken away the radiating 

 rough lines, characteristic of the epiphysial surface, 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 placental Pachy- 

 derms, but resembles in these characters the dorsal vertebrae of the Pro- 

 boscidians ; in these, however, the breadth of the vertebral body is not 

 so great as in the fossil. From the cetacean vertebrae 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, appears 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 the dorsal vertebra of the Megatherioid animal, 

 No. 507, and in the anchylosed lumbar vertebra of the Mylodon, No. 

 398 ; but the bodies of the dorsal vertebrae in all the great extinct Bmta 

 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 Echidna perforates the base of the 

 neurapophyses ; otherwise the body of the dorsal vertebra in that Impla- 

 cental 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 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 depression, which, in the dorsal vertebrae, has no inferior out- 



