ON DIPROTODON 543 
or double strip-like facet, which becomes connected in the middle 
with the worn face of the anterior of the two principal ridges. The 
latter also eventually unite in the middle of the tooth; so that, in 
much-worn teeth, the broad, four-sided field of dentine is surrounded 
only by a narrow band of enamel, the lateral portions of which present 
. two sharply re-entering angles. There is no cinulum continued upon 
either the outer or the inner sides of the base of these teeth. The sur- 
face of the enamel has that sort of “reticulo-punctate or worm- 
eaten” look which is mentioned by Professor Owen as characteristic 
of the teeth in this genus. : 
The first molar is rather smaller than the second: the third is 
wanting: the fourth is considerably longer than the second, as the 
measurements given below will show, and has not the square out- 
line of the first and second; but it diminishes posteriorly by the 
incurvation of its outer contour. Hence the posterior transverse 
ridge of the fourth molar is much smaller than the anterior. The 
tooth is not at all worn, and seems to have been but just cut. The 
principal crests are excavated from side to side posteriorly, and are 
correspondingly convex anteriorly. Superiorly they rise to a minutely 
ridged and forwardly curved edge, which is slightly concave up- 
wards. The anterior basal ridge is sharply defined, but is not so 
thick as in the second molar. 
Each molar tooth has a single posterior fang and two anterior 
fangs. 
The premolar tooth (not more than half the size of the molar 
which succeeds it, and very much less worn) differs somewhat in its 
characters in the two fossils. J will first describe it as it appears 
in No. 1, where the premolar teeth of both sides are preserved. 
The tooth is implanted by two fangs, an anterior, smaller, and a 
posterior, larger ; and its crown has somewhat the form of a tetra- 
hedron with a truncated apex. The posterior side is flat, and slopes 
obliquely forwards to the roof-like summit of the tooth. The outer 
convex surface (fig. 1), is divided into three minor vertical convex- 
ities by two shallow grooves, which cease about halfway towards the 
base of the crown. The inner surface (fig. 3), less extensive than the 
outer, is convex and triangular, being narrower towards the summit 
of the crown. It passes gradually into the anterior side, which is also 
triangular, but still narrower. From the vertical depressions on the 
outer surface two grooves extend inwards on to the crown, which is 
thus divided by two transverse valleys separated by elevations. Of 
these, the two posterior, broad and ridge-like, join internally to form 
the inner surface of the tooth ; while the anterior, which has more the 
