562 
PROFESSOR OWEN ON THE EOSSIL MAMMALS OF AUSTRALIA. 
its middle two-thirds, expanding above and below to the ends of the bone. The fore 
surface of the shaft is smooth, the hind surface shows a shallow narrow longitudinal 
depression (Plate XLVIII. tig. 2, o ; Plate XLIX. fig. 1, o), and near the outer border, 3^ 
inches above the outer condyle, it is 2^ inches in length. A subcircular feebly marked 
rough surface or patch (Plate XLIX. fig. l 5j p) is discernible near the middle of the back 
surface, not quite halfway down the shaft. 
The rotular surface (Plate XLVIII. figs. 1, 2, 4, r) of the distal end, defined by a low 
rising from a slightly depressed fore part of the lower end of the shaft (ib. fig. 1, q), is 
made strongly concave transversely by the forward production of the narrow tuberous 
end (ib. s) of the fore part of the inner condyle ( t ), from which it is divided by a channel 
| an inch wide (ib. fig. 4, ac) continued to the intercondylar pit (u) from the inner surface 
of the distal end of the shaft. The large rotular surface, thus concave transversely, 
convex from before backward, is broadly continuous with the articular surface of the 
outer condyle (ib. figs. 1 & 4, v). The fore-and-aft extent of the inner condyle, including 
the rotular part, is 8 inches ; the same diameter of the outer condyle is but 4 inches 
7 lines. The transverse diameter of the back part of the inner condyle is 3 inches 
6 lines ; that of the outer condyle is the same ; the transverse diameter of both condyles 
(Plate XLIX. fig. 1, t, v ), including the intervening depression (w), is 7 inches 6 lines. 
The form of the articular surface is very different here, in the two condyles ; the inner one 
(£) shows a full convexity in both directions, the transverse contour becoming flattened 
toward the outer border. The outer condyle ( v ) is slightly concave transversely along 
two-thirds of its middle part, the outer convex border being somewhat produced ; the 
outer condyle is also less convex from before backward than the inner one. There can 
hardly be said to be a popliteal depression ; the vertical line of the back of the shaft is 
continued directly into the intercondyloid groove (u), the sides of which are formed by 
the production of the back parts of the condyles. 
The inner surface of the distal end of the shaft developes a strong ridge (Plate XLVIII. 
fig. 5, w), extending above 4 inches from the back part of the inner condyle toward the 
rotular division of the same. The outer supracondylar surface is more even and is 
slightly concave, divided by a moderate rough prominence (ib. fig. 1 ,y) from the smooth 
outer part of the shaft. 
The outer side of the shaft, for a short way below the great trochanter, joins the hind 
surface at an angle, simulating a low ridge continued from the end of the hind lobe of 
that process, and subsiding into the rounded smooth convexity of the outer part of the 
shaft; but there is no “ linea aspera.” I cannot detect in this femur any orifice of a 
medullary artery. The fractured surface of the shaft of a left femur does not indicate 
any medullary cavity. But in the shaft of another femur, corresponding with the above 
in size and shape, the transverse being to the antero-posterior diameter as two to one, 
there is a conspicuous orifice for the medullary artery, at the back part and a little above 
the middle of the shaft, toward the inner side ; the canal slopes upward, to a small sphe - 
roid medullary cavity, with dense walls 1 inch in thickness (Plate XLVIII. fig. 3). 
