432 



two principal transverse lobes in the minor breadth of their outer and inner convex 

 borders as compared with their height were rather those of Sthenurus than of Macro- 

 pus. But Sthenurus Atlas shows no postbasal ridge (comp. Plate LXXXIV. fig. 15, 

 m >, Protemnodon Mimas, with the same view, Plate LXXXI1. fig. 8, of the homologous 

 tooth in Sthenurus). 



On the hypothesis that the specimens (Plate LXXXIV. figs. 13-16 and Plate 

 LXXXVI. figs. 4 & 5) belonged to the same species as the specimen (Plate LXXXV1. 

 figs. 1 & 2), the last, largest and best-preserved unworn molar in the smaller jaws would 

 be homologous with the antepenultimate and worn molar in the larger jaw. The test- 

 scrutiny was accordingly applied, and the germ of the large premolar characteristic of 

 the genus Protemnodon was brought to light in both the smaller fossils (Plate LXXXIV. 

 fig. 14, p 3, Plate LXXXVI. fig. b,]) s). The Kangaroos leaving these remains had each 

 perished at the same phase of dentition as that shown in the type specimen of Sthenurus 

 Atlas (Plate LXXXI1. figs. 3 & 4); the subgeneric characters afforded by the premolar 

 are well exemplified thereby. The comparatively flat undivided outer surface, with the 

 continuous straight trenchant margin of the crown of p 3 in Protemnodon, contrasts with 

 the two convex lobes defined by the median fissure notching the trenchant margin and 

 deeply grooving the outer surface of the crown of p 3 in Sthenurus ; and the differences 

 are better marked in the originals than in the figures above cited, although these give 

 the details with sufficient accuracy. 



The mandibular fossils of the young Protemnodon supply acceptable additional 

 evidence of the dental characters of the species. Thus the crown of d 4, which is 

 mutilated in the type mandible (Plate LXXXVI. figs. 1-3), is entire in figs. 4-6, 

 save as regards the degree of masticatory abrasion to which it has been subject, 

 exposing a linear tract of dentine on each main lobe expanding where the link joins 

 such lobe. The postbasal ridge (Plate LXXXIV. tig. 13, d i) is as conspicuous in this 

 as in the succeeding tooth, m i ; the prebasal ridge shows also a proportionate 

 development, with the fore-link distinct (Plate LXXXVI. fig. 6, d a, s). The first 

 and second deciduous molars (ib. d 2, ds) occupied an alveolar extent of 9 lines; they 

 were displaced, as usual, by the rise of the premolar with a crown of corresponding 

 antero-posterior extent. The subject of figs. 13-15, Plate LXXXIV., was from a 

 younger animal than that of figs. 4-6, Plate LXXXVI. ; in the former the molar (m \) 

 had very recently risen into place ; in Plate LXXXVI. figs. 4-6, the enamelled 

 summits of the transverse ridges of m i are a little worn, as usual, from above downward 

 and backward. 



The socket of the incisor in the subject of fig. 4 is broken across about an inch 

 from its closed end ; the fracture (ib. fig. 8, i) gives, therefore, the breadth and thick- 

 ness of the front tooth at that part, which would be, at least, the same as that of the 

 exserted crown of the large procumbent incisor in Protemnodon Mimas. 



Of the upper jaw and teeth of this species {Protemnodon Mimas) my present evidence 

 consists of photographs of the natural size of a specimen obtained by Professor 



