562 



PKOFESSOE OWEN ON THE FOSSIL MAMMALS OF AUSTEALIA. 



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 XL VIII. 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. 1,^) 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 

 i an inch wide (ib. fig. 4, cc) 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, ^, v), including the intervening depression (m), is 7 inches 6 lines. 

 The form of the articular surface is very difi"erent here, in the two condyles ; the inner one 

 {t) 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 (m), 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. I,^) 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 tliere 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 

 tlic middle of the sliaft, 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. o). 



