44G 



The thin alveolar sheath does not extend to, or has been lost from, the end of the 

 cement-clad root next the enamelled crown. This expands as it extends forward, and 

 terminates in a polished worn surface 10 lines in long diameter (obliquely transverse), 

 5 lines in fore-and-aft diameter. The length of the enamelled (under or outer) part of 

 the crown is 8 lines ; that of the entire tooth is 2\ inches. The fang, as usual, tapers, 

 as it recedes in its socket (Hate CVIII. fig. 4). The narrow symphysial border sinks 

 from the premolar alveolus (ib. fig. 8, I) with a sharp curve before extending forward 

 to expand upon the terminal part of the socket of the incisor (ib. I'). The outlet of the 

 dental canal (v) is nearer the molars, and the diastema, with the symphysial part of the 

 ramus, is longer, relatively, than in Sthenurus Atlas. 



A third example of the premaxillary part of the skull with the fore part of the right 

 maxillary, of a still older individual of Sthenurus Brehus, from Queensland deposits, 

 shows the six incisors in situ much worn, and the form and transverse extent of the 

 palate between those teeth and the molars (Plate CIX. fig. 10). The length of the 

 diastema is 2 inches 1 line ; the breadth of the palate at the prepalatal foramina is 1 

 inch 9 lines. The foramina (ib. a, a) are elongate, from 2 to 3 lines broad, about 6 lines 

 long, and continued forward by a groove (ib. b) which shallows out when parallel with 

 the third incisors. These are much worn ; the working-surface of the third is 7 millims. 

 by 6 millims. The enamel which is continued from the outer upon the hinder surface 

 is impressed, as in the less worn tooth of the younger Brehus, by a longitudinal groove 

 almost equally bisecting the outer surface. The second or mid incisor is worn almost 

 to the stump. The front pair of incisors, being more worn than in the subject of fig. 4, 

 show a working-surface of similar shape but rather smaller dimensions ; the anterior 

 coat of enamel (ib. fig. 1) is reduced to a length of 4 lines (10 millims.). 



In the collection of Marsupial fossils from Queensland, at Worcester, I noted the left 

 lower incisor of a Kangaroo, of which I made drawings of the under or outer side 

 (Plate CVIII. fig. 4). This tooth best agrees with the corresponding incisor of Sthenurus 

 Brehus. It had preserved an extent of enamelled crown of 8 lines, the breadth being 

 that of the more worn incisor of fig. 8. In the great Kangaroo (Macropus major, Plate 

 LXXX. fig. 15) the breadth of the crown of the lower incisor is 4^- lines; in Osphranter 

 rufus (Plate LXVI. fig. 1) it is barely 4 lines. 



The portion of skull of a Sthenurus Atlas (Plate LXXVI. fig. 2, Plate LXXVII. 

 fig. 4) permits comparison to be made of the first and third incisors with those teeth in 

 Sthenurus Brehus. The first incisor is but half the size of that in the larger species, 

 while the third incisor presents a crown of equal size. The generic character of equal 

 division of the crown by the longitudinal groove is retained, but the anterior border of 

 the groove is produced at the lower part of the crown. Such characters, however, may 

 have existed in the part of the crown worn away in the subject of Plate CVIII. fig. 1, i s. 

 But the difference of proportion in the upper incisors is, at least, specific. In Macropu* 

 Titan (Plate LXXVI. fig. 4 & Plate LXXVII. fig. 2) the modification of the pattern 

 of the third incisor is associated with generic distinction in other parts of the dental 



