152 
Fossil Mastodontoid Pachyderm 
lar antcro-posterior compression in the elephant, Mastodon , 
and rhinoceros; but the latter animal is distinguished by a 
second external trochanter, situated below the great trochan¬ 
ter, which is not present in the Australian fossil. In the Me¬ 
gatherium and its congeners the flattening of the femur and 
its transverse breadth greatly surpass the proportions exhi¬ 
bited by the fossil under consideration, or those of the femora 
of the proboscidian Pachyderms. 
The femur of the Mastodon is that which the fossil from 
the Darling Range most resembles, in being flatter on the 
posterior than on the anterior surface. Compared with the 
femur of the Mastodon giganteus , the fossil presents the fol¬ 
lowing differences: it is broader in proportion to its length; 
as, for example, 
Australian femur. Mastodon. 
From the lower part of the post-troclian- 
terian depression to the prominence 
above the outer condyle . 
Breadth of middle of shaft of femur.... 
Circumference of do. do.. 
in. 
lines. 
in. 
lines. 
18 
0 
24 
0 
5 
0 
5 
9 
13 
6 
14 
6 
The surface of the bone below the post-trochanterian de¬ 
pression is more convex in the Australian fossil, and the 
prominence above the back part of the outer condyle is more 
developed ; the small trochanter is narrower and longer, and is 
defined by a groove along its anterior part. The femur in the 
Mastodon giganteus thins off almost to an edge at the outside 
of the distal half of the shaft: in the Australian fossil the 
corresponding part is broad and convex. The anterior part 
of the great trochanter rises higher above the level of that part 
of the femur in the Australian fossil than in the Mastodon, 
The orifice of the medullary artery is conspicuous in the Aus¬ 
tralian fossil at the back part a little above the middle of the 
shaft, and towards the inner side; the canal sloping upwards. 
I cannot detect the corresponding orifice in the Mastodon’s 
femur compared. The Australian fossil exhibits a large me¬ 
dullary cavity along the middle of the shaft, with dense pa- 
rietes an inch thick. The total length of the fossil is twenty- 
two inches; its greatest breadth across the upper or proximal 
end, where the neck begins to bend inwards, is ten inches. 
Traces of the smooth pitted surface at the broken distal end 
indicate the place of junction of the articular epiphysis, and 
prove that the entire shaft of the femur is here preserved ; a 
part of the epiphysis is anchylosed to the shaft. 
The portion ol the molar tooth was obtained from the same 
locality as the femur; and if it belong, as is most probable, to 
the same animal, proves it to be most nearly allied to those 
Pachyderms, as the Pinotherium and Mastodon giganteus, 
in which the grinding surface of the teeth is raised into broad 
transverse ridges. Parts of two ’of the anterior ridges, and a 
