66 
PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
directed downward very slightly forward and outward. The entire tooth (Plate IX. 
tigs. 1 & 2) is 5 inches 1 line long in a straight line, 1 inch 7\ lines in the greatest 
(fore-and-aft) diameter, which is about the middle of the root, 10 lines in greatest trans- 
verse diameter. The enamelled crown (ib. tig. 1, e and 1, b) is 1 inch in length, bevelled 
off, chisel-wise, from before upward and backward, and shows the partial application of 
enamel usual in such teeth: the free margin on the outer side of the crown (fig. 1 ,b) 
extends further back than that on the inner side (fig. 1, e ), and is slightly everted ; it is 
also thicker than on the even inner border. The breadth of the unenamelled back part 
of the crown at its base is 6^ lines. Owing to the difference in extent of enamel on the 
sides of the crown, the abraded surface slopes from without inward and backward, as 
well as from before upward and backward. The enamel is ^ of a line in thickness at 
the outer side of the crown ; the whole outer surface is smooth. The crown is broadly 
convex anteriorly, rather flatter on the inner than on the outer side. The root is thickly 
covered by cement, and increases in every dimension, chiefly from before backward, as it 
recedes from the crown, until at a little below its mid length it attains the dimensions 
above given ; it then diminishes to the pulp end. The outer side begins to be impressed 
by a longitudinal shallow channel about an inch and a half below the crown ; and this 
channel increases in breadth, but not in depth, becoming, indeed, shallower near the 
pulp end of the root. On the inner side (fig. 1) the longitudinal channel begins some- 
what nearer the crown, and sinks deeper as it recedes, besides becoming wider. The 
tooth is compressed and gently recurved, the front margin describing a greater convexity 
lengthwise than is the concavity of the hind margin ; the root contracts to an antero- 
posterior diameter of 1 inch 3 lines; it is slightly excavated by the shallow remnant of 
the pulp-cavity (fig. 1, a). The breadth, owing to the opposite lateral channels, is least 
at the middle of this end, where it contracts to 3 lines ; the part anterior to this gives 
a breadth of lines. 
Thus the first incisor in Nototherium differs from that in Diprotodon not only in 
size, both relative and absolute, in curvature, and in shape, but in structure or in 
kind. It is not scalpriform, not an ever-growing tusk with the enamel continued to 
the widely open base, but is a tooth of limited growth, consisting of a well-defined 
crown and fang. In this character the Nototherium resembles the Kangaroos, whilst 
the Diprotodon shows the Wombat or Rodent type of incisor. 
Of the second and third incisors of Nototherium, nothing more is known to me than 
may be inferred from the sockets indicated in the cast of the skull now at Sydney. 
These seem to show that Nototherium , like Diprotodon, had them of similar and small 
size ; the third not having its enamelled crown longitudinally extended and trenchant 
as in many Kangaroos. The longest diameter of the crown would appear to have been 
6 or 7 lines. 
Of the molars of the upper jaw I have, of Nototherium Mitchelli, the second, third, 
and fourth in situ , in a portion of the left maxilla; the same teeth ( d 4, m i, m 2 ), more 
worn, in a portion of the right maxilla of an older and larger Notothere; and the third 
