248 
PEOFESSOE OWEN ON THE FOSSIL MAMMALS OF AITSTEALIA. 
though not quite to the base; it has an inner basal ridge swelling behind into a 
tubercle, which abuts upon the hinder and larger division of the cleft crown. The 
lower premolar, of smaller size (figs. 4 & 5, p 3), is cleft in a minor degree. 
In Macropus ualabatus the premolar exceeds the adjoining molar (d 4 ) in antero- 
posterior extent. In the upper jaw the trenchant border is slightly notched by a few 
vertical grooves traversing the outer side of the crown ; and the inner basal ridge is 
similarly but more deeply notched ; the entire crown is also broader than in the pre- 
molars of the previously cited species. 
The modifications of the crown in the transversely two-ridged or “ bilophodont ” molars 
add characters in the discrimination of fossils, and it is convenient to define and name 
the parts affording them. The main “lobes” (Plate XX. figs. 29, 30, & Plate XXI. fig. 13, 
m 3) are “front” (a) and “back” (b); a ridge along the fore part of the base of the 
crown is “ prebasal ” (f) ; if, as is usual, there be one at the back part of the crown it 
is “ postbasal” (g, ib. fig. 29, & ib. figs. 12 & 15, m 3). Commonly these several trans- 
verse elevations are connected together by ridges which affect a longitudinal course : 
that which ties the prebasal ridge to the front lobe is the “ fore link ” (ib. fig. 29, & ib. 
fig. 13, m 3, s), that which ties together the main lobes is the “ mid link ” (r), that which 
descends to the “postbasal” ridge is the “hind link” (t), of which ridge it frequently 
seems to be the sole representative (Plate XXI. fig. 18, t ). 
The upper molars, as usual, are broader than the lower ones, and the prebasal ridge 
is usually narrower (antero-posteriorly) ; but the ridge descending from the hinder and 
inner angle of the back lobe to the base of the hind surface of that lobe (“hind link” 
and “ postbasal ridge ”) is usually better marked or more commonly present in the 
upper than in the lower molars. 
The coronal modifications of these teeth are represented in certain existing species 
in figs. 23 to 28, Plate XX. ; to these are added figures of a lower molar in two of the 
extinct species of Kangaroo (ib. figs. 29, 30), which I next proceed to define. 
§ 2. Macropus Titan , Ow. — This species was founded on a portion of the right ramus 
of a lower jaw from the Breccia-cave in Wellington Valley, New South Wales; in 
which jaw, notwithstanding the superiority of size of the molar and of the portion of 
molar in place to any of those in Macropus major, I was led from certain indications of 
immaturity to ask permission from the possessor and discoverer of the then (1836) unique 
fossil to excavate the substance of the bone ; this being granted, led to the detection of 
the nearly complete premolar or successional tooth in its formative alveolus, such as is 
figured in vol. ii. pi. 29. fig. 3 of Sir Thomas Mitchell’s work*. 
The discovery of the premolar was a satisfactory addition to the less conspicuous dif- 
ferences in the molars of the present as compared with those in the fossil jaw of a 
similarly sized extinct Kangaroo, also in Sir Thomas Mitchell’s collection, on account 
of the remarkably large and complex character of the premolar in that fossil, now the 
* Three Expeditions into the Interior of Eastern Australia, &c. 8vo. 1838, vol. ii. p. 360 (2nd edit. 
1839, p. 366, pi. xlvii.). 
