1890.J Identity of Sceparnodon and Phascolonus. 63 



incisors of the so-called Sceparnodon. Of these, the lower jaw and 

 the best preserved of the upper incisors are figured in the accompany- 

 ing Plate. 



The lower jaw (Plate 1, figs. 2, 2a) has been much crushed, 

 and appears to have belonged to an individual just attaining maturity. 

 It contains the third and fourth molars in a perfect condition, the 

 second molar somewhat damaged, part of the root of the first molar, 

 and the base of the incisor. The fragment agrees in all respects with 

 the nearly complete ramus figured in the ' Phil. Trans.' for 1872, 

 PL 36, 37, and, like the latter, shows that Phascolonus differs from 

 living Wombats in the relatively smaller size of the last molar, more 

 especially as regards its second lobe. The Queensland specimen also 

 shows that the mandibular symphysis of the extinct form was much 

 larger, and also relatively wider at its anterior extremity, than in 

 Phascolomys. These features alone would, perhaps, be sufficient to 

 justify the generic separation of the extinct form as Phascolonus, and 

 the great width of the anterior part of the symphysis is especially 

 significant, as being apparently adapted to fit with the wide upper 

 incisors described as Sceparnodon. 



The fragment of the upper incisor represented in figs. 1, la, belongs 

 to the right side, and accords closely with the specimens figured in 

 the ' Phil. Trans.' for 1884, PI. 12, as the types of Sceparnodon, 

 although it is still wider than either of those examples. The cutting- 

 edge is entire, and exhibits the same oblique bevelling on the posterior 

 surface that is shown in two of the specimens figured by Sir R. Owen. 

 Both the anterior and posterior surfaces are covered by a coating of 

 cement, and while there is a well-marked layer of enamel on the ante- 

 rior surface, on the opposite aspect this element is either totally 

 wanting, or reduced to a rudiment. The structure and colour of the 

 cement, enamel, and dentine agree in all respects with those of the 

 molars in the lower jaw of Phascolonus, and, allowing for their 

 greater relative width and flattening, the upper incisors accord in 

 proportionate size with the lower molars, as deduced from a compari- 

 son with a recent Wombat. 



With the foregoing circumstantial evidence before us, I therefore 

 venture to consider that we are now justified in definitely regarding 

 the so-called genus Sceparnodon as based upon the upper incisors 

 of the gigantic extinct Wombat known as Phascolonus. From the 

 great width of the upper incisors as compared with the lower ones, it 

 is pretty evident that the former must have worked somewhat 

 obliquely against the latter. An interesting question arises as to the 

 nature of the food which these excessively wide, and apparently fragile, 

 chisel-like, upper incisors were adapted to cut ; but the answer to this 

 question I must leave to those intimately acquainted with the recent 

 and Pleistocene flora of Australia. 



