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Family GRAVIGRADA. 



Genus Dipkotodon. 



Sp. Diprotodon australis. 



§ 1. Scapholunar bone. — A series of marsupial fossils collected by George Bennett, 

 jun., Esq., at King's Creek, Clifton Station, Queensland, and transmitted to me since 

 the Chapter on Dipeotodontia, pp. 189-248, and its illustrative Plates XIX.-XXXV. 

 were printed off, included the subjects of Plates CXXIL, CXXIII. 



These bones presented proportions and anatomical characteristics new to my experi- 

 ence, and, in ultimate analysis, I was led to refer them to a fore foot of a Diprotodon. 

 An unusually well-preserved mandible of Dipr. australis and some other evidences, or 

 homologues, of parts of the skeleton which had been previously described and figured 

 were in the same series and from the same locality. 



The result of the comparisons of the subject of figures 1-3, Plate CXXIL, was its 

 determination as the left scapholunar bone. 



In the skeleton of a full-grown and large Wombat (Phascolomys latifrons) the 

 answerable carpal bone measures 10^ lines in length ; in that of the Macropus rufus 

 (Plate LXX. fig. 10, /, s) it measures 1 inch 3 lines in length ; the scapholunar of 

 Plate CXXIL figs. 1-3 is 4 inches 5 lines in length ; with it are given corresponding 

 views of a left scapholunar of a large male Macropus major (ib. figs. 4-6). 



In contrasting the mandible of Phascolomys latifrons with that of Phascolonus gigas, 

 and the mandible of Macropus rufus with that of Palorcliestes Azael, the difference of 

 size is so much less than that shown between figures 1 and 4, Plate CXXIL, that the 

 larger scapholunar cannot be referred to the largest known extinct Kangaroo or 

 Wombat ; and after corresponding comparisons of the mandible of Nototherium with 

 that bone in known Macropodes and Phascolomyds, I am led to refer the fossil in 

 question to the still larger extinct form Diprotodon australis. Its proportions to the 

 distal extremity of the radius in that species, moreover, correspond with those between 

 the radius and scapholunar bone in existing Kangaroos and Wombats. 



The radial convex surface (Plate CXXIL fig. 1, a) is ovate in form ; it is broader 

 in proportion to its length than in Phascolomys (Plate XCIX. fig. 5), and in this 

 character our large scapholunar resembles more its homologue in Macropus (Plate 

 CXXIL fig. 4, a). It shows, however, more resemblance to the scapholunar of 

 Phascolomys than to that of Macropus in the limited extent of the dorsal non-articulav 

 tract (fig. 1, b), which has its triangular shape better defined, with the apex projecting 

 between the trapezoidal (e) and the marginal (c) surfaces. That for the trapezoides is 

 relatively smaller than in either Phascolomys or Macropus; and that for the magnum 



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