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In the Kangaroo and the smaller leaping Marsupials the fibula is dispro- 

 portionately slender and immoveably attaehed or anchylosed to the tibia, 

 reminding one of the Ruminant type of organization ; it sustains little if 

 any of the superincumbent weight, and has no resting-place upon the 

 astragalus, the outer malleolus being simply applied to the vertical outer 

 surface of that bone. The broad and nearly horizontal surface in the pre- 

 sent fossil clearly bespeaks the existence in the same animal of a fibula 

 which must have almost equalled the tibia in size at its distal end, and 

 have taken as large a share in the formation of the ankle-joint as it does 

 in the Wombat : we may in like manner infer that the tibia and fibula 

 were similarly connected together, and, coupling this with the ball and 

 socket joint between the scaphoid and astragalus, we may conclude that 

 the foot of the great extinct Marsupial possessed that degree of rotatory 

 movement which, as enjoyed by the Wombat, is so closely analogous to 

 the pronation and supination of the hand. We finally derive from the 

 well-marked marsupial modifications of the present fossil astragalus, a 

 corroboration of the inferences as to the former existence in Australia of 

 a marsupial vegetable-feeder as large as the Rhinoceros, which have been 

 deduced from the inflected angle and other characters of the jaw of the 

 Diprotodon and the Nototherium,and from the fossil calcaneum, No. 1485, 

 which has been referred to the Diprotodon. The present bone closely 

 agrees in all its marsupial modifications with that calcaneum, but the 

 single flat surface which articulated with the calcaneum is longer in pro- 

 portion to its breadth than in No. 1485. From this circumstance and the 

 close agreement in colour and general condition which the present astra- 

 galus has with the jaw of the Nototherium, No. 1505, it more probably 

 belongs to that genus ; but for demonstration further discoveries will be 

 required of parts of the skeleton so associated as to justify the inference 

 that they had belonged to one individual. 



The present bone is from the alluvial or newer tertiary deposits in the 

 bed of the Condamine River, west of Moreton Bay, Australia. 



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



2 t 2 



