788 
PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
nearest approach to the structure in question. It is a large unossified tract of the palate, 
shown in both maxillaries of the fossil (Plate LXXVII. fig. 6, b b) by the passage of the 
palatine (fig. 3 , 21) into the nasal ( n ) plate at a distance of from 2 ^ lines to 3 lines from 
the inner wall of the alveoli of d 4, m 1, and m 2. This upward bend of the palatal plate 
(ib. fig. 3, n ) is at nearly a right angle with the narrow horizontal palatal strip, and in 
both maxillae the continuation of the nasal plate of the maxillary into the orbital one 
by the large spheno-palatine foramen (fig. 3 , s ) is shown. 
Arrested ossification of the palate is, however, a marsupial rather than a macropodal 
character, and is exemplified, in my “ Osteology of the Marsupialia” *, in the Thylacine, 
the Sarcophile, the Dasyure, the Bandicoots, the Peragale, and the Potoroo, as well as in 
a small species of Kangaroo ( Halmaturus Bennettii). In this species the palatal vacuities 
are four in number, in two lateral pairs f. In Halmaturus brachyurus (Plate LXXVII. 
fig. 1, b b) the intervening strip of bone between the fore and hind vacuity is wanting, 
and each pair is blended into one large lateral unossified tract, which either falls into its 
fellow, or is separated from it by a mere filament of bone. Such was the structure in 
the great procoptodont Kangaroos, the vacuity, moreover, extending more forward than 
in Halmaturus or Petrogale. 
I need scarcely say that the dentition of the small existing species of these genera is 
of the ordinary halmatural type ; the premolar is trenchant, the inner ridge being low 
or ‘ basal.’ 
The front pier of the zygoma (Plate LXXVII. figs. 2-5, 21 ', 21 "), extending from the 
fore part of the orbit obliquely downward and backward, terminates below, in the pre- 
sent immature specimen of Procoptodon, above the interval between d 4 and m 1 ; it might 
recede in relative position to the molar series when this was fully in place ; but so much 
of the pier as is preserved is more compressed, and stands out relatively further than in 
any existing Kangaroo. I shall subsequently be able to show that the more advanced 
position of the descending masseteric process is constant at all ages in Procoptodon, and 
may be added to the palatal and dental characters of the genus. 
§ 6. Procoptodon Pusio. — These characters, as above defined, added to size, exem- 
plify the present species. 
The antero-posterior extent of the three molars d 4, m 1 , m 2 , Plate LXXVII. in the 
subject of figures 2, 3, 6, is 1 inch 10 lines ; the four teeth, the premolar being in 
place, would reach along 2 inches 4 lines : taking the fore-and-aft diameter of the last 
molar, m 3, to equal that of the penultimate one, m 1, here in place, the permanent 
upper molar series of Procoptodon Pusio (ib. fig. 7) would be 3 inches 2 lines in 
longitudinal extent. All things being equal this Kangaroo was one third larger than 
Osphranter robustus , Gd. J 
§ 7. Procoptodon Baplia, Ow. — The size of the premolar (Plate LXXVII. fig. 8, p 3) 
in the fragment of lower jaw of the immature Procoptodon next to be described indi- 
* Zoological Transactions, 4to, vol. ii. part 1, 1838, p. 388, plates 70 & 71. t Op. dt. pi. 71. fig. 5. 
t Compare figure 7, Plate LXXYII. with figure 3, Plate xxi., Philosophical Transactions, 1874. 
