PROFESSOR OWEN ON THE EOSSIL MAMMALS OE AUSTRALIA. 
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great proportion of fragmentary evidences of the hind feet of large extinct Kangaroos 
as compared with entire or nearly entire bones. The grateful aid which such rare 
specimens have yielded has impressed me with the desirability, if not duty, of defining 
and recording all characters which may help future collectors, especially in Australia, 
in determining such fossil fragments which are likely to accumulate in the public and 
private museums of that great colony. 
I refrain from trespassing on the time and means of the Society with the results of 
comparisons by which metatarsals of Macropus Titan , of the two dentally determined 
species of Sthenurus, and of some species of Protemnodon have been worked out. But, 
in regard to the extinct form of Kangaroo which has most interest in relation to its 
aberrant or transitional character, I cannot withhold evidences which give some clue 
to the characters of the hind limbs, and I finally pass to the result of the present 
researches which has yielded me perhaps most satisfaction. 
I have alluded to the primary step in the survey of the vast series of metatarsal 
fossils which led to setting apart those indicative of a hind foot shorter in proportion to 
its breadth, and yet retaining unmistakable macropodal characters. 
In the specimen, for example, of the naturally united fourth and fifth metacarpals 
figured in Plate 31. figs. 1-5, the fourth is thicker than, but is little more than two 
thirds the length of, the homologous bone in Macropus rufus (Plate 29. fig. 4). The 
fifth metatarsal (Plate 31. figs. 1, 2, 3, v) shows a greater degree of thickness, in pro- 
portion to its length, than in Palorchestes Azael (Plate 29. figs. 1 & 2, v). 
The proximal end of the fourth metatarsal (Plate 31. fig. 4, iv), though somewhat 
mutilated, exhibits the characteristic modifications of the articular surface in the normal 
Kangaroos ; and these characters are shown more plainly in the homologous bone of a 
larger kind of Procoptodon (ib. fig. 8, iv), viz. the non-articular peninsula (/), the back- 
ward or plantar production ( e ), with the terminal groove (g 1 ) for the tendon before 
mentioned ; but this groove is less deep than in the type Kangaroos : the flat surface 
beneath (fig. 6, h) indicates a larger proportional sesamoid than in the species of 
Macropus. 
The fore surface of the shaft of the fourth metatarsal (ib. fig. 2) is more even or 
flattened than in Macropus affinis, Macr. Titan , and the great recent kinds of Kan- 
garoo. The distal end is more expanded, surpassing the proximal end in breadth. 
The ridge on the back part of the shaft (ib. fig. 1, o) is broader, less produced, and less 
extended downward than in Macropus , Sthenurus , or Palorchestes. 
The well-preserved proximal end of the fifth metatarsal shows its apophysial pro- 
duction (ib. figs. 1 & 2, z) proximad of the articular surface of the fourth metatarsal. 
This process is absolutely as well as relatively longer than in Palorchestes Azael. As 
in that species three articular facets are present at this end of the bone, two for the 
cuboid and one for the contiguous (fourth) metatarsal, the cuboidal surfaces being 
relatively larger than in Palorchestes , and the tubercle projecting tibiad beyond the 
metatarsal surface is more developed in Procoptodon. 
2 h 2 
