528 
PROFESSOR OWEN ON THE EOSSIL MAMMALS OF AUSTRALIA. 
ably large proportion of the symphysis in Diprotodon to the size of its molar teeth there 
are no quadrupeds which so nearly resemble it as the Notothere and the Wombat; but 
in this existing Marsupial the symphysial part of the jaw is broader in proportion to its 
depth. The long and narrow symphysial junction in the Kangaroo is peculiar for the 
yielding movements allowed to the rami upon each other, which is betrayed by those 
of the long procumbent depressed incisors in the living animal*. 
§4. Dentition . — The dental formula of Diprotodon is: — i~, c~, m^= 28. Of 
the upper incisors the first or anterior pair (Plate XXXV. figs. 1 & 2, i 1 ; Plate 
XXXVI. figs. 1-6) are large curved scalpriform teeth, of which I have not found indi- 
cations of cessation of growth in any specimen. The skull above described and figured 
(Plate XXXV.) has been that of an aged male, judging from the size and degree of attri- 
tion of the teeth which are retained ; but the anterior incisors above, like the pair below, 
are continued to the bottom of their deep alveoli without contraction, and with the re- 
tention of a widely open pulp-cavity (Plate XXXVI. fig. 6). It is obvious that these 
,-strong anterior incisors (ib. figs. 1-4) worked with the evergrowing power of the “ dentes 
scalprarii” of the Wombat, the Aye-aye, and the Rodents. 
In the above skull the length of i 1, following the convex curve of the tooth, is 11 
inches; its circumference is 4 inches 9 lines; the breadth of the oblique abraded 
working surface is 1 inch 9 lines ; the longitudinal extent of that surface is 2 inches ; 
but this varies in other specimens. An extent of the tooth of 8^ inches (following the 
outer curve) is lodged in the socket of the premaxillary. 
I made a transverse section of a fragment of the skull of a Diprotodon, including the 
fore part of the premaxillaries and their scalpriform teeth (Plate XXXVI. fig. 5). Such 
section of the tooth (i 1, c, d, e) is irregularly three-sided, with the angles broadly rounded 
off. The inner side, or that next the fellow tooth, is the narrowest ; the front or ena- 
melled side is the broadest : this side is traversed lengthwise by a wide and shallow mid 
channel ; the opposite side is grooved by a narrower and rather deeper channel, running 
along its outer half ; and the inner more prominent half of this side (the concave one 
lengthwise) also shows a narrow and feeble impression near the mid-line of the tooth, and 
a broader more shallow impression nearer the angle, dividing the hinder from the inner 
surface. This surface, 1 inch 3 lines across (ib. fig. 2), is generally somewhat convex, 
but wavy through two or three low obtuse longitudinal ridges, with intervening shallow 
channels. A fossil fragment of a similarly sized tooth yielding such transverse section 
as that shown by this remarkable scalpriform incisor would, according to present expe- 
rience, determine the genus of Mammal to which it had belonged. 
The enamel coating the anterior convex curve of the tooth is continued over the major 
part of the outer rounded surface, terminating abruptly along a line (ib. fig. 5, d) 
external to the outer longitudinal ridge (c) of the posterior surface. In like manner 
the enamel is continued over the rounded angle between the anterior and inner or me- 
dial sides of the incisor, and terminates abruptly at e, fig. 5, after covering about one- 
* First noticed by Mason Good, ‘Book of Nature,’ vol. i. p. 283. 
