OAVEN NOTOTHEEIUM. 181 



From the e\T.denee of the ramus of the jaw in question, it thus 

 appears that the genus Nototherium, as represented by the smaller 

 species, Not. inerme, was characterized by at least five molars in each 

 mandibular ramus, and by a procumbent incisor, of less relative 

 size than in Diprotodon ; its socket not extending back beneath the 

 anterior molar. 



From the Diprotodon the Nototlienum differs, in both Not. inerme 

 and Not. MitcheUi, in the poKshed surface of the enamel, as con- 

 trasted with the re ticulo -punctate surface of enamel in the corre- 

 sponding teeth of Diprotodon. Nototherium also differs in the oblique 

 production, or ridge, from the outer and fore part of each lobe of the 

 molar ; by which it approaches nearer to Macropus, where such 

 ridges are more developed. 



The second species of Nototherium (N. MitcheUi) was founded on 

 the posterior half of the left ramus of the lower jaw, now in the 

 Museum of the Eoyal College of Surgeons (jS'o. 1506, Catal. of 

 Foss. Mam. 4to, p. 316, 1845), containing the last two molar teeth, 

 which differed in their more advanced position, in reference to the 

 coronoid process, from the Not. inerme. In a collection of Aus- 

 tralian fossil remains, lately acquired by the British Museimi*, there 

 is an almost entire lower jaw (Plate IX. figs. 1 and 2), the hinder 

 half of the left ramus of which precisely corresponds in size and 

 shape with that of the Nototherium MitcheUi, and the fore part of 

 which also shows the first small single-rooted molar ; and in advance 

 of its socket, the base of that of a procumbent iucisor, having the 

 same small relative size as compared with Diprotodon, which the 

 lower jaw of the Nototherium inerme exhibits. The condyloid, 

 coronoid, and angular processes, together with the fore part of the 

 symphysis, are broken away in this specimen. 



The back part of the ascending ramus below the condyle is 

 bent or produced inwards, so as to form a deep concavity on the inner 

 side of the base of that process. The inward production subsides, 

 however, before it reaches the ordinary position of the angle of the 

 jaw, from which it is separated by a smooth tract, where the outer 

 surface is continued into the inner surface, without any production. 

 Below this, the thick posterior and inferior border of the ascending 

 ramus is again bent inwards, but in a rather less degree than the 

 part above. The depression on the outer side of the coronoid process 

 much resembles that in Nototherium inerme; but the fore part of 

 that process commences at a greater distance external to the alveolar 

 tract, as well as being opposite to the back instead of the middle part 

 of the last molar tooth. A low ridge is continued from the middle 

 of the back part of the socket of that tooth backwards to the process 

 marked h in figs. 2 and 3, plate 4, of my origiual memoir on the 

 genus NototheHum, and which is described there as " a broad platform 

 of bone on the inner side of the base of the coronoid process." The 

 entry of the dental canal is situated behind this platform, close to 



* At an auction at Messrs. Stevens's, King Street, Covent Garden ; and stated 

 to have belonged to a Mr. Boyd. 



