182 PKOCEEDINGS OE THE GEOLOGICAL SOCIETY. 



the coronoid process, and distant from the last alveolus 2 inches 9 

 lines. The coronoid process has the same extensive fore and aft 

 origin, and the sHght transverse diameter as in Nototherium inerme, 

 but is rather more concave externally. 



The outer side of the horizontal ramus of the lower jbm of Not. 

 Mitchelli is as convex as in Not, inerme ; but it has a greater relative 

 depth compared with the size of the molar teeth : this depth taken 

 at the mid part of the last molar in Not. Mitchelli is 3 inches 9 lines : 

 in Not. inerme it is only 2 inches 10 lines. 



The long (fore and aft) diameter of the last molar in Not. 

 Mitchelli is 1 inch 10 lines: the breadth of its front lobe is 

 1 inch 5 lines. The hind lobe is narrower. The cingulum is 

 interrupted on the inner end, but not on the outer end of this 

 lobe, behind which it swells into a talon of two lines breadth. The 

 cingulum is interrupted at both the outer and inner ends of the 

 front lobe, and is reduced in breadth where it is overlapped, at the 

 outer half of the fore part of the tooth, by the talon of the next 

 molar. The two ridges show the same degree of anterior concavity, 

 and oblique production, of their outer and front angles as in N. 

 inerme. 



The penultimate molar is 1 inch 9 lines in long di'ameter, 1 inch 

 4 lines in breadth ; it closely corresponds with that tooth in Not. inerme, 

 but has been more abraded in the present specimen. The antepenul- 

 timate or third tooth (Plate IX. figs. 1 and 2) is 1 inch 6 Imes in 

 long diameter, 1 inch 2 lines across the hind lobe, which is rather 

 the largest. 



The socket of the second tooth {ih. d 4) indicates it to have had a 

 long diameter of 1 inch 3| lines. The first tooth (ih. p-i) was, 

 apparently, but 5 lines in long diameter, and was implanted by a 

 single fang. 



The extent of the five sockets is 7 inches 3 lines ; that of the last 

 three sockets is 5 inches 2 lines; the same extent is 5 inches 

 in Nototherium inerme. 



The back part of the symphysis in Nototherium Mitchelli is oppo- 

 site the interspace between the third and fourth molar; in Not. 

 inerme it is opposite the middle of the third molar. A longitudinal 

 extent of 5 inches 3 lines of the symphysis, i. e. for 1| inch in ad- 

 vance of the first molar, is preserved on the left side of the lower 

 jaw here described; and beneath this part the alveolus 0^ the 

 procumbent incisor penetrates to a depth of 1 inch 9 lines: and 

 that socket indicates a somewhat relatively larger incisor than in 

 Nototherium inerme ; yet one much less, both absolutely and relatively, 

 than in Diprotodon. What the entire length of the symphysial part 

 of the jaw has been in advance of the molar series cannot be deter- 

 mined, owing to the unfortunate fracture of that part in the present 

 specimen. 



The total length of the left ramus (mutilated at both ends) is 1 

 foot 2 inches. The breadth of the mandible across the first molar 

 alveolus is 2 inches 6 lines; but the jaw swells out as it descends. 

 In front of this alveolus the jaw contracts suddenly at its upper 



