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PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
ridge (Plate XXIV. fig. 6,/’) without a fore link ; by a still narrower and shorter post- 
basal ridge, represented by that, g (fig. 4 a), which curves from the outer part of the 
base to the inner angle of the hind lobe, along the back part of the crown, that surface 
sinking a little above the part of the ridge nearest the base of the tooth. The mid link 
(ib. fig. 6, m 3, r) is thin, low, or rudimental, yet still traceable from the back part of 
the inner angle of the anterior lobe to the middle of the base of the fore part of the 
hind lobe. The contour of the working-surface of the molars is more subquadrate 
than in Macropus Titan, the fore-and-aft diameter being not so much greater than the 
transverse. The series describes a feeble curve convex outward, but changes anteriorly 
to a slight concavity through the modification of the premolar at a, as above described. 
The abraded state of d 4 contrasts with the almost untouched crown of p 3 , showing the 
earlier development of the hinder tooth. The dentine is just exposed on the inner 
halves of the lobes of m i. The enamel only shows abrasion at the summits of the lobes 
of m 2 ; the edges of those of m 3 are slightly polished by wear anteriorly. This fossil 
has come from an individual that perished in the prime of life. 
In existing Kangaroos the upper premolar of Macropus ualabatus , Lesson (Plate 
XXIV. figs. 1-3, p 3), bears the nearest resemblance to that of Sthenurus Atlas, and is 
associated with the same general pattern of working-surface of the molars d 4, m 1-3, 
except that the fore link and mid link, though feebly developed, are more neatly defined 
and readily recognizable in the small existing Kangaroo. The figures of both these 
recent and fossil Kangaroos, or “ Wallabies,” being of the natural size, preclude the need 
of stating dimensions. 
Macropus ( Sthenurus ) Atlas was first indicated by a fragment of the under jaw from 
the Breccia-cave in Wellington Valley. In the type specimen (Plate XXII. figs. 3 & 4) 
three molars (d 3, d 4, and m 1) are in place ; the penultimate molar ( m 2) is lost ; the 
crown of the last molar (m 3) is just rising from the formative alveolus. 
The first true molar (m 1) affords an instructive comparison and contrast with that in 
the type specimen of Macropus Titan (ib. figs. 17, 18, 7m). The grinding-surface of 
m 1 in Sthenurus Atlas is broader in proportion to its length, especially behind. The 
prebasal ridge is narrower and lower ; a simple link descending from the fore and outer 
angle of the front lobe slopes straight to the middle of the summit of the prebasal 
ridge. 
The outer convex borders of the two lobes (ib. fig. 4, m 1 ) are narrower than in 
Macropus Titan (ib. fig. 18, m 1 ), and maintain their breadth, like columns, more uni- 
formly to their summits. The inner borders are rather broader below, but are narrower 
than in Macropus Titan. In Sthenurus Atlas the valley between the lobes is both wider 
transversely and deeper, the link being lower; it slopes from a point rather external to 
the middle of the front surface of the hind lobe, and runs almost straight down to the 
middle of the base of the hind surface of the front lobe. The mid link becomes almost 
obsolete in the last molar (ib. fig. 3 , m 3). The summits of the lobes bend slightly back- 
ward vertically, and from the thickening of the outer and inner angles are feebly concave 
