274 



10 lines in greatest transverse diameter. The enamelled crown (ib. fig. 1, e and 1, h) 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 C>^ 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 somewhat 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 anteroposterior 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 oppo- 

 site 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 4^ 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 too'th 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 

 and fourth in situ in a fragment of the right maxilla of a younger specimen. The entire 

 molar series of both sides is shown in the cast of the skull in the Australian Museum 

 (Plates XXXVI. & XXXVII.), and the left series in the cast of the left maxilla of another 



