OWEN NOTOTHEEITTM. 179 



cess. The base of the inflected angle is continued for 2 inches 

 forward and inward from the same fractured base, and there is a 

 well-marked depression on the inner side and above the base of this 

 marsupially inflected angle: a little in advance of it the lower 

 border of the ramus has been produced and slightly bent inwards, 

 for the extent of 4 inches, as far forward ' as the penultimate 

 molar : owing to its degree of production, which, however, was pro- 

 bably not great*, this inflected ridge or border has been broken 

 away. 



The posterior inlet of the dental canal commences at the back 

 part of the thick convex rising which is continued forward on the 

 inner side of the ascending ramus to the inner side of the last al- 

 veolus, and which rising divides the inner coronoid surface above 

 from the surangular depression below: the foramen is situated 2 

 inches behind the last molar tooth, and on a rather higher level than 

 the border of its alveolus : internal to it are a groove and a ridge : 

 it is elliptical in shape, and 5 lines long in diameter : a smooth 

 tract, concave lengthwise, of more than an inch, divides the ridge 

 and the process from the inner and hinder part of the last alveolus, 

 which process has been broken away, together with the border of 

 the alveolus and the crown of the last molar. 



The fore and aft extent of the last four molar teeth is 6 inches. 

 Each of these teeth is implanted by two fangs. The fractured sur- 

 face of the jaw in front of the first of these two-fanged teeth (Plate 

 IX. fig. 3) shows the back part of the smooth vertical socket of a 

 small anterior molar, of which no trace is perceptible in the some- 

 what more mutilated ramus, specimen No. 1505, on which (in the 

 Museum of the College of Surgeons) the species Notoiherium inerme 

 was foundedf. The fractured anterior surface of the mandibular 

 ramus under description shows also the back part of the socket of a 

 procumbent incisor, which alveolar surface, or bottom of a socket, 

 is in advance of that of the first small molar. 



The character of the Nototherium inerme, as originally given in my 

 ' Catalogue of Fossil Mammalia' and ^ Report,' &c., must be rectified 

 by the addition of a fifth molar — the small anterior one ; and of an 

 incisor, shorter and relatively smaller than that of Diprotodon, in 

 each ramus of the lower jaw. 



The fore part of the dental canal is exposed immediately external 

 to the back wall of the incisor socket, where it is reduced to the 

 diameter of 3 lines. 



The depth of the ramus of the jaw behind the symphysis is 3 

 inches ; and it is the same behind the penultimate molar. The 

 thickness of the ramus behind the symphysis is 1 inch 8 lines ; 

 but it iucreases by the convex outswelling of the outer surface to 

 2 inches 3 lines behind the penultimate molar. 



The crown of the last molar (fig. 3, ms) has been broken away ; 

 its base measures, in length 1 inch 10 lines, in breadth 1 inch 



* According to the analogy of Nototherium Mitchelli, specimen No. 1506 

 Mus. CoU. Chir., where this ridge is entire. 



t ' Catalogue of Fossil Mammalia,' Mus. Coll. Chir. 4to. 1845, p. 314. 



N 2 



