Prof. Owen on an Incisor of Nototlieriuni Mitchellii. 475 



LXI. — On an Upper Incisor 0/ Nototherium Mitchellii. 



By Professor R. Owen, F.R.S. 



[Plate XVI.] 



To the Editors of the Annals and Magazine of Natural History. 



Gentlemen, 



I have received, through the kindness of Sir Daniel Cooper, 

 Bart., from the freshwater beds of Gowrie Creek, Darling Downs, 

 Queensland, an upper front incisor, right side, of the Nototherium 

 Mitchellii (PI. XVL), which so closely accords in size with the 

 dimensions of the tooth described and figured in the December 

 Number of your volume xvi. (1865) p. 448, by Prof. M^Coy, 

 that I am disposed to ascribe that tooth also to the species near 

 the remains of which it was found, " at Murchill, not far from 

 Geelong, Victoria." 



My specimen 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 transverse 

 diameter. The enamelled crown, e, is 1 inch in length, be- 

 velled off, chiselwise, from before downward and backward, 

 and shows the partial application of enamel usual in such 

 teeth ; the free margin on the outer side of the crown (fig. 4) 

 extends further back than that on the inner side (fig. 1 e), 

 and is slightly everted : it is also thicker than the even 

 inner border. The breadth of the unenamelled back part of 

 the crown (figs. 1, 3, 4 d) 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 above downward and backward. The enamel is 

 ^ oi 2i. 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 more thickly covered by cement, and increases in 

 every dimension, chiefly from before backwards, as it recedes 

 from the crown, until at a little below its midlength 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, 4)ut not in depth, be- 

 coming, indeed, shallower near the pulp end of the root. On 

 the inner side, the longitudinal channel begins somewhat 

 nearer the crown, and sinks deeper as it recedes, besides 

 becoming wider. The tooth is "compressed and gently in- 

 curved," or, rather, "recurved," the front margin describing 

 a greater convexity, lengthwise, than the hind margin : the root 



