798 
PEOFESSOE OWEN ON THE FOSSIL MAMMALS OF AUSTEALIA. 
and Sthenurus it exceeds, d 4 in that dimension. But in the fossil the transverse diameter 
of the premolar in proportion to the length of the crown is greater than in any known 
existing Kangaroo, and in this respect is equalled only by the extinct Procoptodons. As 
in these, also, the front pier of the zygoma (ib. 2 i») has a more advanced position in rela- 
tion to the molar series than in Macropus , Osphranter , or Halmaturus. But the chief 
distinctive character of the present fossil is the great proportional length of the pre- 
maxillaries (Plates LXXXI.-LXXXIII. 22 , 22 ') and the concomitant backward position 
of the incisive or premaxillary palatine foramina (ib. a), which are closer together, and 
were separated by narrower processes of these bones, if so separated at all ; for the 
foramina in the fossil seem to have been confluent, and were certainly short and parallel ; 
whereas in Macropus , Osphranter , Halmaturus, and Petrogale (Plate LXXVII. fig. 1, 
a a) they are relatively longer, are wider apart, and usually with their narrow or 
pointed hind ends convergent. 
The dental formula, i 3-3, c 0, m 5-5, and pattern of the grinding-surface of the molars 
(Plate LXXXII. fig. 2) being macropodal, the differential characters from known 
recent and fossil Kangaroos are of subgeneric value, and call for the usual taxonomic 
indication which heads the present section. 
§ 10. Palorchestes Azael, Ow. — The fore end of the premaxillaries is not quite entire, 
but sufficient of the sockets of the three incisors of the right side remain to show that 
not more than half an inch of the bone can there be wanting ; the teeth have dropped 
out prior to fossilization. From the fore end of the skull to the premolar ( p 3) is * 
5 inches ; the length of the molar series is 4 inches 6 lines. These two admeasurements 
are relatively almost the same in Osphranter robustus, the length of its series of five 
molars being 2 inches 2 lines, and that of the skull in advance of the premolar being 
2 inches 3 lines ; the part of the skull behind the last molar in the fossil is 2 inches 
9 lines in length. On this basis the entire skull of Palorchestes Azael may be 
reckoned at about 16 inches in length. 
The extent of the diastema in the upper jaw supports an inference of a like extent in 
the lower, and would show a nearer resemblance, in the latter respect, of Palorchestes to 
Macropus, Osphranter, and other genera of normal Kangaroos, than to the extinct 
Sthenuri, Protemnodons, and Procoptodons, which, in their shorter and deeper diastemal 
and symphysial part of the mandible, exemplify the transition to Nototherium. 
The extent of the premaxillaries ( 22 ) from the alveolar outlets to the anterior bony 
nostril ( n ) is relatively greater than in any skull of a living Kangaroo I have yet seen 
(compare fig. 2 with fig. 3, Plate LXXXI.). The tract in question slopes backward as it 
rises and curves, more vertically near the nostril, where it swells into a pair of low 
tuberosities (ib. fig. 1, n). So far the union of the two premaxillaries is close, seem- 
ingly anchylosed, though the mid line of their symphysis is traceable. In this character 
Palorchestes offers a resemblance to the Koala and Wombat*. A little behind the 
tuberosities each premaxillary sends upward its plate to form the outer walls of the 
* Philosophical Transactions, 1872, Plate 11 . figs. 3 & 4. 
