z58 
PEOFESSOE OWEN ON THE FOSSIL MAMMALS OF AUSTEALIA. 
the right and left rami was not more close in the large Macropus Titan than in Macropus 
major. The direction of the elongated socket of the incisor and the procumbent 
position of that tooth in the fossil are as in the existing species of Macropus. The 
crown of the incisor, so far as it is preserved, agrees in shape, relative size, disposition 
of enamel, position and obliquity of the back part of the abraded working-surface, with 
that of Macropus major. The configuration of both outer and inner surfaces of the 
horizontal ramus, especially the ridge indicating the lower limit of insertion of the crota- 
phyte muscle and extending a little lelow the margin of the ectocrotaphyte cavity, as 
shown in Macropus major (Plate XX. fig. 15), are repeated in Macropus Titan (Plate 
XXII. fig. 13, e). The last molar stands out more freely, or entirely, in advance of the 
fore margin (ib. fig. 13, q) of the coronoid process in Macropus Titan than in Macropus 
major (Plate XX. fig. 15) ; and it advances further as the animal grows older and the 
molar series is further reduced. 
The inflection of the inner and lower border of the ascending ramus begins anteriorly 
nearly in the same relative position. The anterior border of the intercommunicating 
vacuities (Plate XXII. fig. 15, e, d ) between the outer and inner cavities of the ascending 
ramus appears to be the same in the present fossil as in the largest existing species of 
Kangaroo. The inner postalveolar border is smoothly rounded, and forms no angle 
indicative of a postalveolar process. 
The molars in the fossil under description are more worn than in the Macropus major 
compared, with a similarly reduced series of teeth. In d\ (Plate XXII. fig. 14) the 
exposed tract of dentine is continuous, the mid link crossing the valley being worn 
through. The prebasal ridge is indicated only by the internal notch ; the basal remnant 
of the crown is supported by fangs, which are partially exposed by absorption of the 
alveolus, and the crown overhangs the beginning of the diastema, indicative of the im- 
pending fall of the tooth (ib. fig. 13, <2 4); whence I infer that the molar dentition of 
Macropus Titan would be reduced in advanced age, like that in Macropus major, by the 
loss of d 4, and perhaps ultimately of m 1*. 
The pattern of the working-surface of the succeeding molars closely accords with that 
in Macropus proper. The prebasal ridge is considerable, both longitudinally and trans- 
versely: the fore link is well marked ; it joins the front lobe external to the mid line, 
leaving a fossa on each side. The contrast with the rudiment of this link in Sthenurus 
Atlas (ib. figs. 8 & 9) is considerable, as is that also in the development of the mid link 
and the breadth of the anterior margin of the prebasal ridge. 
The antero-posterior breadth of the transverse ridges is greater in Macropus Titan 
than in Sthenurus Atlas, especially at their outer sides (comp. figs. 13 & 5) ; the 
longitudinal extent of the crown is relatively greater as compared with the transverse 
diameter in Macropus Titan. 
In the next illustration of the mandibular characters of Macropus Titan, so much as 
is preserved of the two rami shows the angle at which they meet to unite at the sym- 
* Since this passage was penned I have received from my friend Dr. Bennett, F.L.S., evidence of the fact. 
