Mastodonioid Pachyderm in Australia. 



second external trochanter, situated below the jrreat 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 fe- 

 mora 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 giyanteits^ the fossil presents the fol- 

 lowing differences : it is broader in proportion to its length ; 

 as, for example, 



Australian femur, 

 in. lines. 



From the lower part of the post-trochan- 

 terian depression to the prominence 



above the outer condyle 18 



Breadth of middle of shaft of femur . . 5 

 Circumference of do. do. . . 13 6 



The surface of the bone below the post-trochanterian de- 

 pression [b) 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 Au- 

 Fig. 2. Fig. 3. 



stralian 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 Austrahan fossil exhibits a large me- 



