1877.| PROF. OWEN ON A NEW SPECIES OF STHENURUS. 355 
logous, but here median, longitudinal ridge. In sum, the upper 
and long premolar in Dorcopsis, like that of the short premolar of 
Dendrolagus, is generically distinct in its modifications from that of 
the premolar in the three known species of Sthenurus. 
In the upper molars of Sthenurus the prebasal ridge is relatively 
larger than in Dorcopsis and Dendrolagus, the mid link is better 
developed ; there is an increase of breadth from the first (d4) to the 
third (m2) molar in Sthenurus not shown in Dorcopsis (comp. 
figs. d4, m3 in Plate XXXVII. with fig. 2, pl. vii. P.Z.S. 1875). 
The generic type of the lower premolar is still more marked in 
Dorcopsis (ib. plate vii. fig. 3) and Dendrolagus as compared with 
its homologue in Sthenurus (Plate XXXVIII. figs. 9, 10, 16, 17) ; 
this is manifested in the latter genus by the bilobed character of the 
outer surface, conspicuously shown in the unworn, unexcluded crown 
of the tooth in the type species of the genus (Sthenurus atlas)’. 
In Dorcopsis the outer surface, like the inner one, of the lower 
premolar retains the simple vertically grooved surface as in the Po- 
toroo type (Hypsiprymnus). The tendency to that modification of 
Macropodal structure is further shown by the retention of the canines, 
though minute, in the upper jaw, by the predominance in size of the 
foremost upper incisor, 2 1, and the production of its cutting surface 
beyond or below the horizontal line of wear of the two following in- 
cisors (¢2,73). The canines are relatively larger in Dendrolagus, as 
in the Hypsiprymnine. 
IT have not found an upper canine in a Sthenurus of any age. In 
the fossil of the young Sthenurus atlas (the subject of plate xxv. 
fig. 2, Phil. Trans. 1876), with the deutition less advanced than in 
the present evidence of Sthenurus minor, the maxillo-premaxillary 
suture shows no trace of such tooth or of any socket of a shed rudi- 
_ ment; yet the foremost incisor was not fully in place, and the crown 
of the third incisor required for exposure the removal of the premax- 
illary alveolar wall. The character of the crown of 7 3, so detected, 
enabled me to determine the detached homologous teeth of old 
individuals of Sthenurus atlas. In all the pattern is distinct from 
that of 73 in either Dorcopsis or Dendrolagus. Subsequent acquisi- 
tions of premaxillaries and their teeth of the larger species, Sthenurus 
brehus, showed the same generic character (plate xxviii. figs. 1, 3, 
11,72, 73, Phil. Trans. 1876). The outer or labial surface of the 
crown of 73 is equally bisected by a subvertical linear groove or 
enamel-fold; the fore-and-aft breadth of the unworn crown exceeds 
that which appears in the side view of ¢1 (Plate XXXVIII. fig. 11) 
in Sthenurus atlas, and equals the total breadth of that tooth. The 
three incisors on each side work on the same horizontal level. 
In all these characters Sthenurus deviates from the Halmaturine, 
Dorcopsine, and Hypsiprymnine types, and approaches that of the 
great Kangaroos represented by Macropus proper, Osphranter, and 
Boriogale (Phil. Trans. 1874, plate xx. figs. 17, 18, 19). 
« Mitchell’s ‘ Three Expeditions into the Interior of Eastern Australia,’ 8vo, 
1838, plate xxix, fig. 1; Phil. Trans. 1874, pl. xxii. figs. 4, 5, 6, p3, pl. xxiv. 
fig. 7, p3. os 
