301 



the fragment, which is six inches long, presents no appearance of a 

 medullary cavity. This fossil has the same general colour and heavy 

 mineralized condition as the portions of the jaw of the Diprotodon austra- 

 lis, Nos. 1460 and 1461. 



From the alluvial or newer tertiary deposits in the bed of the Conda- 

 mine River, west of Moreton Bay, Australia. 



Presented by Lieut. -Col. Sir T. L. Mitchell, C.B. 



1482. A fragment of the shaft of a long bone of the same size and texture as 



the preceding, and perhaps forming part of the anterior wall of the same 

 tibia. 



From the alluvial or newer tertiary deposits in the bed of the Conda- 

 mine River, west of Moreton Bay, Australia. 



Presented by Lieut. -Col. Sir T. L. Mitchell, C.B. 



1483. A fragment of the shaft of one of the long bones of the extremities, 

 apparently the tibia, of a large quadruped : the exterior shows a portion 

 of two almost flattened surfaces meeting at an open angle, from which a 

 short rough ridge-like process is developed ; at the upper part of this 

 ridge the orifice of the medullary artery is situated, the canal of which 

 expands as it slightly descends to gain the medullary cavity ; no part of 

 that cavity is distinctly visible in the fossil ; the compact part of the wall 

 is half an inch thick, and a moderately close cancellous texture is con- 

 tinued inwards from it ; at the upper part of the fragment the compact 

 wall is about a quarter of an inch thick ; the breadth of the fragment, 

 which seems to include about one-fifth part of the circumference of the 

 bone, is two inches and a half. The ridge, near which the medullary 

 artery penetrates the tibia in the larger Pachyderms and Ruminants, is 

 situated at the confluence of two surfaces of the tibia, which meet a much 

 less open angle than in the present fossil : in the Giraffe the correspond- 

 ing angle is rounded off. In the Elephant and Mastodon the medullary 

 artery perforates the bone at the middle of the flattened posterior surface 

 of the tibia. In the Kangaroo the ridge near which the arterial orifice 

 is situated is much more acute and more produced than in the fossil. In 

 the Wombat the corresponding orifice is situated at the ridge where the 



