PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
563 
The femur, like the pelvis, of Diprotodon presents the greatest resemblance in general 
form and characters to the corresponding bone in Proboscidia. The head is devoid of 
the ligamentous pit ; the shaft is straight and antero-posteriorly compressed ; there is 
little* or no medullary cavity. 
Passing to particulars of structure, there appear several more or less well-marked 
differences. 
The head rises higher above the neck and trochanter in Elephas ; it has a more directly 
upward aspect, the neck is shorter, the great trochanter is absolutely, as well as rela- 
tively, of less extent in Elephas. The trochanterian depression is less deep, and opens 
nearer the exterior surface of the trochanter. A ridge is continued downward from the 
border of the depression, which, with a second ridge continued downward from the outer 
part of the trochanter, bounds a flat facet forming the outer surface of the upper half 
of the shaft : there is no such definite facet in Diprotodon. At the upper and fore part 
of the trochanter in Elephas there projects a tuberosity midway between the head of the 
femur and the outer part of the trochanter, and the neck rising to support this tube- 
rosity is somewhat convex transversely : there is no trace of this tuberosity in Dipro- 
todon, and the fore part of the neck is concave transversely. The small trochanter, 
which in Elephas , as in Diprotodon, is a long longitudinal ridge, is situated lower down in 
Proboscidia. The ridges continued from the great trochanter upon the shaft represent, 
in that order, “ linese asperse,” of which there is no trace in Diprotodon. 
The differences become more marked at the lower end of the bone. The rotular 
surface or pulley is absolutely as well as relatively narrower in Elephas ; it has a more 
anterior aspect, is supported on an anterior production or expanse of the femur ; the 
sides of the pulley are parallel, subequally developed; there is no production of the 
inner one as in Diprotodon. The outer as well as the inner part of the rotular articular 
surface is distinct from that surface in the corresponding condyle. Both condyles are 
convex and equally prominent behind in Elephas ; in which genus there is no trans- 
verse hollowing of the outer condyle, giving a trochlear character with production of 
the outer border of that condyle as in Diprotodon. The intercondylar groove is deeper 
and narrower in Elephas than in Diprotodon. 
Omitting the notes of comparisons of the femur of Diprotodon with that in other large 
quadrupeds, the essential correspondence throwing true light on the determination of 
the species to which it belongs, and the affinity of that species, is found in the Poephaga 
or Macropodidce exclusively. It is there only that one finds the transverse excavation 
of the surface of the outer femoral condyle, producing the contrast of a trochlear cha- 
racter of surface with the uniform convexity or ball-like prominence of the inner condyle. 
In the Great Kangaroos ( Macropus major , M. laniger) the character is exaggerated, the 
channel is deeper, and its outer border is more produced. The rotular surface is broad, 
with unsymmetrical sides in Macropus, the inner border being sharpest, though less 
produced anteriorly than in Diprotodon. 
* See Osteological Catalogue of the Museum of the Royal College of Surgeons, 4to, p. 481. 
