PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
787 
the undeveloped and unextricated premolar (ib. figs. 2, 3, 4, y 3) ; it was so far advanced 
as to have pushed its crown to near the level of the base of d 3, at the interval between 
the diverging pairs of the fore and hind fangs of that deciduous tooth (ib. fig. 6, d 3). 
The major part of d 4 had been broken away on the right side, but the crown remained 
in the left maxillary. The mid link and the accessory ridge are here present, and the 
hind surface of the second lobe shows the complex accentuation, which is further 
carried out in the succeeding teeth. On the summits of both lobes of d 3 and d 4 the 
dentine had been exposed by masticatory abrasion. 
The thin smooth partition-wall between the sockets of m 2 (the hindmost tooth in place) 
and of m 3 was manifest at the back part of each maxillary (fig. 5 , m 3), confirming, 
with the more decisive evidences at the fore part, the homologies of the more or less 
complete teeth, and demonstrating the immaturity of the individual from which the fossils 
had been derived ; the usual process for exposing the premolar had the usual result. 
The crown of the premolar (ib. figs. 2, 3, 4, p 3, and fig. 7, p 3), in its antero-posterior 
extent, resembles that of Macropus proper, not being quite equal to that of the crown of 
the next tooth (d 4) ; but it is thicker transversely than in Macropus or Sthenurus, with a 
transversely ridged complexity of the broad working-surface between the outer (a) and 
inner ( b ) longitudinal ridges or walls (fig. 7), which shows it to have acted as a pounder 
rather than a divider of the vegetable food, a character which suggested the name pro- 
posed for the genus (Note *, p. 786). 
The vertical extent of the enamelled crown of the premolar does not exceed the 
breadth of the hind part of the tooth. The outer surface shows three conical elevations, 
in low relief, of the enamel, one behind another (fig. 2, p 3). The apex of the foremost 
constitutes the anterior prominence of the outer longitudinal ridge ; that of the second 
slightly projects from the middle of that ridge (a, p 3, fig. 7) ; that of the hindmost one 
subsides before it gains the ridge, which is continued, sharply, upon the outer and back 
part of the crown of the premolar. The foremost of the three conical low reliefs of the 
enamel forms the outer part of the fore swollen end of the crown (fig. 4 ,p 3), which is 
divided by a depression from the lower and narrower, basally swollen beginning of the 
inner longitudinal ridge (J). This slightly diverges as it recedes from the outer ridge, 
obeying the hinder enlargement of the crown, and it is united near that end by a trans- 
verse ridge with the outer longitudinal one. The transverse ridge is a miniature or 
rudiment of a hind lobe, and its hind surface is excavated and ridged in a feeble or 
rudimental way like that part of the normal hind lobe of the bilophodont molars. The 
horizontal triturating surface of the premolar between the outer and inner longitudinal 
ridges is sculptured by transverse sharp enamel-ridges and deep depressions. 
There is a character in the upper jaw of Procoptodon which is not present in the 
large existing Kangaroos of the subgenera Macropus and Osphranter. It is present, 
under some modifications, in Boriogale and in the smaller Kangaroos or Wallabies 
of the subgenera Halmaturus and Petrogale. I find, indeed, in Petrogale xan- 
thopus, Gd., and Halmaturus brachyurus, Wth. (Plate LXXVII. fig. 1, b b), the 
