999 
PE0FESS0E OWEN ON THE EOSSIL MAMMALS OE AUSTEALIA. 
At the distal articular surface the chief difference is seen in the greater production 
of the tibial convexity of the trochlea. By reason of this prominence its preservation 
is rare in the rolled fossils of the present form of metatarsal from the creek-beds of 
Queensland. 
Of the metatarsals of this shorter type three modifications are shown by the fossils 
that have reached me, which are indicative of three species of Procoptodon. The 
metatarsal (Plate 31. figs. 10-12), of equal length with that (ib. figs. 1, 2) of Procoptodon 
Pusio, but more slender, I take to be from a female Kangaroo of that species. 
Deeming it probable that the form (family or genus) of Macropodal Marsupials 
which, by dental and mandibular characters, offered the nearest approach to the large 
isopodal or gradatorial family ( Diprotodontidce ) would present a corresponding approach 
thereto in the form and proportions of the hind foot, I refer the present type of meta- 
tarsal bones to the genus Procoptodon. 
In this genus the above-described representative of the smallest known species would 
answer, as to size, to the evidences which have been given of the maxillary, mandibular, * 
and dental characters of Procoptodon Pusio*. 
The specimens next in size (Plate 31. figs. 6-9) I refer, on similar grounds, to 
Procoptodon Papha f. 
Parts of a hind foot of a still larger species similarly relate to Procoptodon Goliah $. 
Save in size, the characters of the metatarsal about to be described so essentially 
resemble those of the homologous bone in Plate 31, that I have not thought it reason- 
able to devote to it an additional Plate. 
This metatarsal, the fourth, is 5 inches 3 lines in length, with a proximal breadth of 
1 inch 5^ lines, the opposite dimension being 1 inch 3 lines. The fore part of the 
cuboidal surface is relatively broader from before backward than in Procoptodon Pusio. 
There is no indication of the proximo-tibial ridge (x, fig. 10, Plate 30), in which cha- 
racter the present bone resembles its homologue in Procoptodon Papha. 
The posterior angle at the proximal half of the shaft is less marked and less produced 
than in Procoptodon Pusio. The posterior depressions above the distal trochlea are 
deeper and better defined than in Procoptodon Papha or Procop. Pusio. 
The fifth metatarsal of Procoptodon Goliah is 5 inches in length ; the greatest dia- 
meter of the shaft is 1 inch, equalling that of the homologous bone in Palorchestes 
Azael, which is more than one fourth longer. The tibial covexity of the distal trochlea 
is less produced than in Procoptodon Papha, and the whole hind surface of the joint is 
less obliquely disposed than in that species or in Procoptodon Pusio. 
Thus the resolution of these shorter and stouter metatarsals into three categories, 
characterized by modifications of shape as well as by size, concurs with the previously 
adduced evidences of jaws and teeth in showing that the procoptodont modification of 
Macropodidoe was of old manifested by Australian Kangaroos under three specific forms. 
* Phil. Trans. 1874, p. 788, plate lxxvii. figs. 2-7. 
t Ib. p. 788, plate lxxvii. figs. 8-12, plate lxxviii. 
i Ib. p. 791, plates lxxix., lxxx. 
