1877.] PROF. OWEN ON A NEW SPECIES OF STHENURUS. 353 
nent series of upper molars is 3 inches 4 lines’. In Osphranter 
rufus this series is 2 inches 3 lines, reduced by loss of the premolar 
to 2 inches (asin Trans. Zool. Soc. vol. ix. pl. 74. figs. 1 and 3); and 
these dimensions are not exceeded in Macropus major. 
The extinct Kangaroo, represented by thesubjects of Plate XX XVII. 
somewhat exceeded the above largest known existing species. The 
fragment of skull is a little larger than the corresponding part of a 
full-grown Macropus major, with the last molar in place and use 
and the premolar shed; it consists of both maxillaries with their 
respective (right and left) molar series, the intervening bony palate, 
and a portion of the right orbit and zygoma with the descending 
masseteric process. 
The dentition is in an instructive phase. The left series of grinders 
shows the premolar (ib. fig. 1), p 3, in place, and the last molar, m 3, 
protruding from the formative cell. The right series shows the 
deciduous predecessors (d 2, d3) of p 3 in place, and m 3 less advanced 
than on the left side. Thus there are five functional grinders on the 
right side and four on the left side of the upper jaw. The formula 
of the left series is p3, d4, m1, m2 (m3 not fully emerged); the 
formula of the right series is d2, d3, d4, mi, m2 (m3 less advanced). 
Accordingly the outer parietes of the right maxillary were removed 
above d 2 and d 3 with the usual result, the crown of p 3 and beginning 
of its roots becoming exposed in the formative cell (Plate XX XVII. 
fig. 2, p 3). 
The fore-and-aft extent of the left permanent series of upper molars 
is 2 inches 10 lines, that of the four bilophodont molars (correspond- 
ing with those shown in the skull of Osphranter rufus, Trans. Zool. 
Soc. tom. cit.) is 2 inches 3 lines; but the inferiority of size of the 
present species of Sthenurus to the two previously known species sug- 
gested the ‘‘nomentriviale.” Sth. minor, however, surpasses in size 
any known existing Kangaroo, but is the smallest known of its genus. 
In the comparisons required for taxonomic conclusions as to these 
large extinct Kangaroos, I found, in 1873, the nearest approach to 
the character of the premolar of Sthenurus in some small Kangaroos 
of the genus Halmaturus, and I figured the dentition of H. walabatus® 
(Phil. Trans. tom. cit. plate xxiv. figs. 1, 2, 3, 10, 11, 12) as show- 
ing the nearest resemblance to that of S. atlas (ib. ib. figs. 4, 5, 6, 
7,8). But the premolar of the Halmaturus, with the same general 
type, had less relative antero-posterior extent, and had not the 
smaller deep-seated transverse ridges; the bony palate also, as in 
other Wallabies, presented a pair of large vacuities. Subsequently ° 
I was enabled to show a more marked generic distinction in the form, 
sculpturing, and proportions of the upper and outer (third) incisor. 
In 1874, M. D’Albertis described and figured a small existing 
kind of Kangaroo under the name of Halmaturus luctuosus*, obtained 
© Phil. Trans. 1874, p. 272, pl. xxvii. figs. 5-9. 
» Lesson, not Gray ; the latter is probably a variety of Halmaturus rujficollis, 
Desm. 
3 Phil. Trans. 1876, p. 211, pl. xxv. figs. 2, 3, pl. xxviii. figs. 1, 3. 
+ Proceedings of the Zoological Society, 1874, p. 110, et p. 247, pl. slii. 
Proc. Zoou. Soc.—1877, No. XXIII. 23 
