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femur ; least so at the upper, and most at the back part of the process, where the border 

 defines outwardly a small but deep trochanterian fossa (ib. f). This fossa is bounded 

 below by a small tuberosity. The small trochanter is represented by a rough ridge 

 6 inches long, 2 inches broad, occupying the middle third of the shaft a little anterior to 

 its inner border. A few shorter longitudinal ridges occur on the fore part of the shaft 

 between the upper end of the small, and the upper and fore part of the great trochanter- 

 The rest of the anterior surface of the femur is smooth, concave lengthwise, slightly 

 convex transversely. 



The back part of the femur presents a small low tuberosity below its middle part, 

 near the inner border ; the triangular surface between this tuberosity, the head, and the 

 great trochanter, is smooth and flat. The contour of the back part of the femur, from 

 the head to the outer condyle, is convex ; that from the trochanter to the inner condyle 

 is concave ; the lower half of the back part of the shaft is convex transversely. The 

 lower end of the femur (Plate XXIV. fig. 2) presents two articular surfaces, the inner 

 one (ib. i) being that of the internal condyle, the outer one being the combined ectocon- 

 dyloid (e) and rotular (r) surfaces. The latter is extensive, and describes a semicircle 

 from before backward, but is narrow from side to side : in this direction the rotular portion 

 is slightly concave ; its limits are indicated by a notch on the inner side : the condyloid 

 portion is slightly convex transversely, in which direction the extent is scarcely 2-J inches. 

 The entocondyloid surface (i) is of nearly twice that breadth ; is of a reniform shape, 

 and is convex in every direction. The intercondyloid channel is roughened by decus- 

 sating ligamentous impressions and ridges, with some vascular pits. Its narrowest part 

 is anterior, and measures an inch and a half across ; posteriorly it is 3 inches across. 

 The intercondyloid border of the inner condyle is sharply defined and projects below 

 the level of the canal, that of the outer condyle is mostly on a level with the canal. 

 The surface of the canal meets the hind surface" of the femur at almost a right angle, 

 the intervening ridge being rounded off. The fore part of the inner condyle stops short 

 of the fore part of the shaft ; the back part of the condyle projects 1 inch beyond the 

 back part of the shaft. The process or prominence above the inner condyle (eminentia 

 entocondyloidea, Plate XXIII. fig. 1, ie) forms an obtuse angle, the lower side of which 

 is rough, rather flattened, and expands as it descends towards the articular part of the 

 condyle. The outer condyle does not project so far back as the inner one : its supra- 

 condyloid prominence (ec) is larger, of a similar angular form, but is bent forward as 

 well as outward. 



In the Elephant, Mastodon, and Diprotodon, the shaft of the femur is flattened from 

 before backward ; but the length of the femur so far exceeds its breadth, that, strong 

 as the thigh-bones of these quadrupeds are and well-proportioned to the weight they 

 had to sustain, they appear weak and even slender when placed by the side of the femur 

 of the Megatherium. The Rhinoceros, which has the thigh-bone relatively broader 

 and flatter than in the proboscidian pachyderms, differs more markedly from the Mega- 

 therium in the presence of the third trochanter. 



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