PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
63 
The symphysial joint in Nototherium Victoria? has become completely obliterated in 
the present full-grown specimen ; a dense, minutely spongy tissue is included in a thin 
compact crust of bone. 
The inner wall of the alveolar outlets does not rise so high as the outer one ; it thins 
off to an edge closely fitting the contour of the base of the crown of the tooth ; the 
inner side of the horizontal ramus (fig. 2) at once descends with a gentle vertical con- 
vexity, interrupted beneath the last and part of the penultimate sockets by the concavity 
due to the inflected lower border (d, d'). The depth of the inner side of the ramus 
behind the fifth (last) socket is 2 inches 9 lines; in Nototherium Mitchelli it is 3 inches 
6 lines. 
The portion of the base of the incisor-socket exposed by the anterior fracture (fig. 4, i) 
gives a vertical extent of 1 inch, a transverse breadth of 4 lines. The bottom is smooth ; 
the side-walls worm-eaten, with a tendency to longitudinal striation. External to this 
part of the socket, about a line’s distance, the dental canal is exposed, of a subcircular 
section, 3 lines in diameter ; about the same thickness of the osseous tissue divides it 
from the outer surface of the jaw. Two inches behind this part a small orifice pierces 
the outer surface at the same distance below the middle of the outlet of the alveolus of 
the molar (m i, fig. 1). 
The colour of the fossil above described from the deposits near Lake Victoria is a rich 
brownish yellow. The osseous tissue is massive, the bone heavy, but does not adhere to 
the tongue. The minute cancelli are vacant, not filled up by mineral matter. The dental 
canal contains the easily displaced lacustrine deposit. The Nototherian fossils from 
Darling Downs are either of a deeper and duller brown colour, as in the first described 
jaw (Plate IV.), or of a greyish mottled stone-colour, as in the third and fourth speci- 
mens. 
C. Nototherium inerme , Ow. — The fossil (Plate VIII.) on which the species Nototherium 
inerme is founded consists of a left ramus of the lower jaw, mutilated and abraded as in 
most of the specimens from the river-beds and deposits of Queensland. The base of the 
coronoid (fig. 1,/), with the entry of the dental canal (fig. 3, o) and part of the inflected 
angle (ib. b , e), remain at the hind end of the specimen, and the back part of the sym- 
physis (figs. 2 & 3, s) terminates the fore end. The symphysis does not extend back- 
ward beyond the vertical parallel of the fore half of the second molar ( d 4). The dental 
canal (fig. 3, 0 ) begins near the level of the molar, and 1 inch 9 lines behind the last 
alveolus. In the type mandible of Nototherium Mitchelli , as in the subjects of Plates 
IV. & V., the orifice of the dental canal is raised above the level of the grinders, and 
is 3 inches behind the last alveolus; yet the antero-posterior diameter of that alveolus 
is less in Nototherium Mitcltelli than it is in N. inerme. The specific difference of 
N inerme from both N. Mitchelli and N Victories is also shown in the relative position 
of the symphysis to the fully developed molar series. The absence of any trace of inci- 
sive alveolus at the fractured part of the symphysis indicates the tooth to have been 
relatively smaller, still less of the character of a tusk or weapon offensive or defensive ; 
