PROFESSOR OWEN ON THE EOSSIL MAMMALS OE AUSTRALIA. 
205 
large frontal sinuses has been obliquely crushed. The specimen is in the usual heavy 
petrified condition of fossils from the freshwater drift ; it shows the effects of trans- 
port and attrition during the movements of this matrix before reaching the locality 
where it was found. 
The first attention being directed to the teeth, of which the three last left molars 
and the four last right molars were in place, the characters of transverse lobes, links, 
and prebasal ridge were seen to be those of the genus Macropus , while the size and 
the sculpturing of the hind surface of the last molar (Plate 26. fig. 2) determined the 
species. 
In Macropus major that surface (ib. fig. 3) is moderately hollowed lengthwise and 
thickly coated with cement, which partly fills the triangular transverse concavity, the 
apex of which shallows to the ordinary level of the hind surface before reaching the 
base of the crown. When the cement is removed the inner enamel boundary (fig. 3, g) 
is sharper and more produced than the outer one (ib. h). 
In Macropus Titan the enamel, after coating the inner border of the hinder lobe, 
extends backward, downward, and outward, projecting as a sharp-edged ridge (ib. 
fig. 2, g), defining a deeper depression on the hinder surface of the tooth. There is 
also a shallow vertical groove ( h ) continued from the hind part of the apex of the inner 
border of the hind lobe downward toward the base of the crown, which groove seems 
to define the inner limit of the oblique posterior ridge. One sees that this groove 
repeats the deeper cleft that defines the mid link internally from the inner end or 
border of the anterior lobe. The oblique hind ridge (g) is indeed a serial repetition of 
the mid (r) and fore (s) links, but subsides with a more oblique course downward 
toward the base of the outer border of the hind lobe, having no other division of the 
molar to connect with such lobe. From the fore part of the base of the inner end of 
the hind lobe a low ridge defines the anterior surface of that lobe to the inner side 
between it and the mid link ; this defining ridge is not present in the upper molars of 
Macropus major , but there is a small tubercle at the inner entry of the valley between 
the two main lobes of the upper molars in Macropus major which is not present in 
Macropus Titan. 
The fossil skull, with the molars agreeing in the above characters and in size with 
those of more fragmentary examples of Macropus Titan*, is of a mature and somewhat 
aged individual. The summits of both lobes of the hindmost grinder are worn so as to 
expose a linear tract of enamel, widest of course on the anterior lobe. In the penulti- 
mate grinder a broad field of dentine is exposed on this lobe, extending backward by a 
linear tract along the base of the mid link (r), but not so far as the transverse tract of 
dentine exposed on the hind lobe. In the antepenultimate grinder (m i) both lobes are 
so worn that the lozenge-shaped fields of exposed dentine touch and communicate at the 
base of the worn-down link. The foremost grinder ( d 4, Plate 26) is retained on the 
right side, worn down to its base ; but this tooth has been shed on the left side, and 
* Phil. Trans. 1874, plate xxi. figs. 8, 10, 15, 16 ; plate xxii. figs. 10, 12. 
2 f 2 
