256 
PEOFESSOE OWEN ON THE FOSSIL MAMMALS OF AUSTEALIA. 
Of the mandibular dentition of Macropus Titan an early stage is exemplified in the 
fragment of lower jaw from the Breccia-cave of Wellington Valley on which the species 
was founded*. 
I have given an improved figure of the outer side of this specimen, with the pre- 
molar exposed in the primitive alveolus, in Plate XXII. fig. 18, and have added a view of 
the grinding-surface of the two mutilated molars in situ ( ib. fig. 17). This portion of 
(right) mandible of Macropus Titan includes the hind part of the first molar ( d 4 ) and a 
larger proportion of the succeeding molar (m i). The anterior lobe of this tooth is 
entire ; the hind part of the posterior lobe is broken away. 
The anterior talon or “ prebasal ridge ” of m i has almost the character of a lobe ; it is 
united to the anterior normal transverse lobe by a well-developed fore link, commencing 
near the outer angle of the fore lobe, and describing a slight bend in its forward course 
to expand upon the hind part of the “ prebasal ridge” nearer its outer than its inner 
end. The projecting angle of the “ link ” is directed inward. The valley between the 
anterior lobe and the prebasal ridge is thus divided into two hollows, the inner one 
being the largest. The inner border of the prebasal ridge is sharp, and abuts against 
nearly the middle of the back part of the antecedent tooth ( d 4). The outer border of 
the prebasal ridge is thicker than the inner one, less inclined inward, and projects 
freely a little external to the level of the hind lobe of d 4. The back part of this lobe 
is entire ; it shows a submedian posterior vertical indent ; there is no perceptible trace 
of basal ridge. 
The mid link (fig. 17, Plate XXII.) repeats the characters of the fore link, save that it 
sinks lower to connect itself with the anterior lobe, leaving more of the summit of that 
lobe free than is left to the prebasal ridge. The summit of the anterior ridge of m 1 
inclines a little forward as it crosses the tooth from without inward, and is slightly 
bent with the convexity backward. The mark of wear, which in the young animal 
owning this tooth had not exposed the dentine, affects the hinder slope of the summit 
of the transverse ridge. 
The characters of the crown in the two lower grinding-teeth of the type specimen of 
Macropus Titan above described are, in the main, those of the largest existing repre- 
sentatives of the true or subgenerically restricted Macropus. ' 
In the lower jaw of Macropus major (Plate XX. fig. 15) the prebasal ridge (fig. 16,/) 
of m 1 and m 2 has a like size and shape, and is connected with the anterior lobe by a 
similar link ; but this is less bent inwardly in its. forward course. In Macropus rufus 
the prebasal ridge is less developed (Plate XXI. fig. 4) ; there is no postbasal ridge or 
talon. A feeble vertical notch is shown by the back part of m 1 and m 2 ; this does not 
* Three Expeditions, 8vo, 1838, by Sir Thomas L. Mitchell, C.B., vol. ii. p. 359, pi. xxix. fig. 3. This 
specimen, with other fossils from the Wellington Yalley cavern, submitted by its discoverer to me, were pre- 
sented to the Geological Society of London, to the President and Council of which I am indebted for the 
opportunity of reexamining and figuring this collection, which initiated our knowledge of the fossil Mammals 
of Australia. 
