784 
PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
The only difference of note is in the more advanced position of the last molar ; and 
this is due to the well-known general forward movement of the serviceable teeth when 
those anterior to them have been worn down and shed — a movement which reaches its 
maximum in the Elephants. 
§ 2. Macropus Ferragus , Ow. — A portion of a right mandibular ramus with the last 
- two molars in place and worn (Plate LXXXI. fig. 4, and Plate LXXXII. figs. 3 & 4) 
indicates, both by the size of the teeth and that of the jaw itself, a Kangaroo too much 
exceeding in size the largest individuals of Macropus Titan to belong to that species. 
A comparison of the above-cited figures with figures 13, 15 in Plate xxii. of the previous 
Part* will demonstrate this fact. 
The jaw-bone of Macropus Ferragus is relatively thicker in proportion to the teeth, 
and the last molar (Plate LXXXII. fig. 3, to 3) rises more in advance of the origin of 
the coronoid process ; but this may relate to the greater age of the individual as shown 
by the exposure of the dentine in both lobes (ib. fig. 4) of that tooth, though they are 
not worn to quite the same degree as in fig. 2, Plate LXXVI. The base of the notch 
(Plate LXXXII. fig. 4, g) remains on the hind part of to 3, and internal thereto are 
indications of two vertical ridges which I have not found in any fossil of Macropus Titan . 
§ 3. Pachysiagon'f Otuel$, Ow . — In the portion of right mandible with the three 
hindmost molars (Plate LXXVI. figs. 7-10), in which the dentine is exposed on the 
summits of the lobes of to 3 and in the usual proportionally greater degree in to 2 and 
to 1, the three molars, corresponding in fore-and-aft extent with those in Macropus Titan 
(Plate xxvi. fig. 9, Philosophical Transactions, 1874), and only exceeding by a line 
the same teeth in the subject of figure 11, Plate xxvi., ib., are implanted in a jaw 
of considerably greater thickness. This jaw likewise shows a wider ectalveolar channel 
(Plate LXXVI. fig. 9, u) ; the anterior border of the base of the coronoid also rises 
more vertically and more in advance of the last molar, a difference not to be accounted 
for by age, as is manifest in a comparison of the present fossil with the mandible in 
younger individuals of Macropus Titan. 
With these mandibular indications of, at least, specific distinction, the molars them- 
selves show the following differences. The prebasal ridge does not extend so far 
forward as in Macropus proper; the hind surface of the molars has two vertical 
narrow grooves, to which a third shorter and feebler one is added in to 3 (ib. fig. 10, g). 
These grooves do not extend below the base of the transverse lobe, and below them the 
common base of the crown of the tooth rises smoothly and convex for a line and a half 
clear of the socket ; the innermost notch is very little deeper or wider than the next — 
contrasting strongly with the large and deep notch on the inner half of the hind surface 
of the molars in Macropus Titan , which descends nearer to the origin of the hind fang 
of the tooth. 
Another character is shown in the mid link (Plate LXXVI. fig. 9 ,r), which sends off 
* Philosophical Transactions, 1874, p. 245. f From Tra^s, thick ; oiaywv, jaw-bone. 
+ A giant in the ‘ Romance of Roland and Ferragus.’ 
