250 
PEOEESSQE OWEN ON THE EOSSIL MAMMALS OE ATJSTEALIA. 
d 3 ; its crown would then contrast with that of d 4 by its freshness or freedom from wear. 
The convexity of the outer surface of the two lobes, and the depth of the dividing in- 
dent, accord with the characters of the lower premolar of the type specimen of Macropus 
Titan expressed in fig. 18, Plate XXII. 
The bilophodont* upper molars of Macropus Titan (Plate XXI. fig. 8) show a well- 
developed “ prebasal ridge ” connected by a “ link ” of enamel with the fore part of the 
front lobe, near the middle and inclining rather toward the inner angle. In Sthenurus 
Atlas (Plate XXIV. fig. 6) this link is feebly if at all developed. 
The mid link connecting the two main lobes in Macropus Titan (Plate XXII. fig. 11) 
is rather sinuous and tumid; it is better developed in this species than in Sthenurus 
Atlas (Plate XXIV. fig. 6). The oblique posterior ridge (Plate XXII. fig. 11, to 3, g , 
and Plate XXI. fig. 9, m 2) is strongly marked, and defines a depression at the inner and 
under side. The main lobes have broad convex bases in the side view of the molars, 
and the entire crown is longer in proportion to its transverse breadth than in Sthenurus 
Atlas. 
The front pier of the zygomatic arch (Plate XXI. fig. 6, av) is in advance of the hind- 
most molar in place (to 2) in this young specimen. The anterior outlet of the suborbital 
canal (ib. fig. 6, 21) is 9 lines in advance of the orbit. Behind the outlet (21) is the small 
orifice (a) of a (vascular \) canal, descending into the substance of the maxilla. I have 
not observed this orifice in the large existing Kangaroos. So much of the bony palate 
as is preserved (ib. fig. 8) is entire aud imperforate, as in Macropus major. This cha- 
racter, associated with the small size and simple structure of the premolar, and, as will 
be seen in subsequently described fossils, its comparatively early loss, support a reference 
of the present large Kangaroo to the genus Macropus, as restricted by most zoologists 
of the present day. 
In the specimen from the Breccia-cave, Wellington Valley, of the left upper maxilla 
and molar series (Plate XXI. fig. 10) the premolar had risen into place ; the last molar 
(to 3) was protruding from the formative cell, but had not come “ into line ; ” the first two 
deciduous molars had been shed. 
The crown of the foremost tooth was broken off, but the fangs remained (ib. p 3). They 
were two in number (the hindmost the largest), corresponding in relative size, degree of 
divarication, and extent of jaw occupied by their insertion with those developed in the 
unprotruded premolar of the younger specimen (ib. fig. Q,p 3). The choice of the tooth 
belonging to the fangs in front of the series in the subject of fig. 10 lies between^? 3 and 
d 3 ; but the latter tooth has, in conformity with its broader bilophodont crown, four 
roots, each pair diverging from a transversely extended base. The evidence of the roots 
remaining in the socket of the broken molar is therefore decisive of its homology; 
the loss of the crown of p 3 is nevertheless regrettable. Its working-surface would have 
contrasted with that of the tooth d 4, which, having been longer in place and use, 
* This term signifies not only that the crown is composed of two principal ridges or lobes, but that these 
are transverse in position. 
