hatcher: diplodocus (marsh) 



47 



the bone so as to occupy the same plane as the external and internal condyles of the 

 distal end. By reason of this a femur of Diplodocus when lying on a plane surface 

 with posterior surface down will be supported by the head and external and internal 

 condyles, while a femur of Brontosaurus lying in the same 

 position would have the head directed obliquely upward and 

 free from the supporting surface. The shaft in cross section is 

 flattened antero-posteriorly and somewhat elongated trans- 

 versely, Avith the internal surface deeper' than the external, so 

 that the cross section is ovate in outline, tending to form dis- 

 tally a more or less perfect ellipse. The greater trochanter is 

 not distinctly separated from the head and the rugose surface 

 of the latter is continued uninterruptedly and covers the supe- 

 rior surface of the greater trochanter. There is a faint con- 

 striction, but no well-defined neck connecting the head with 

 the shaft of the femur. The external and internal condyles 

 are large and well separated by a deep intercondjdar groove. 

 The external is divided into two parts, one external and the 

 other internal, by a deep posterior median groove which doubt- 

 less served for the transmission of a strong tendon. The third 

 trochanter is present, but small. Internal to and directly 

 alongside it there is a small but quite rugose flat surface for 

 increased muscular attachment. The third trochanter in 

 Diplodocus is not homologous with the game trochanter in 

 mammals. It is situated on the inner and posterior margin 

 in Diplodocus instead of on the outer as in mammals, when 

 present. In mammals it curves forward, while in Diplodocus it 

 is directed directly backward. Figs. 15 and 16 represent re- 

 spectively the proximal and distal extremities of a femur, No. 

 94, of Diplodocus, while lateral and front views are given in PL 

 XI., Figs. 3 and 4, and an oblique internal front view is shown 



in Fig. 17. 



Fig. 17. Oblique in- 

 ternal front view of left 

 femur of Diplodocus car- 

 negii (No. 94). ir., third 

 trochanter. About one 

 eleventh natural size. 



Measurements of No. 84. 



Greatest length 1542 mm. 



" breadth at proximal end 500 " 



" " " distal " 412 " 



No. 94. 



Greatest length 1470 mm. 



^' breadth at proximal end 390 " 



" " "distal " ..365 " 



61| 



in. 



17i 



Li 



16J 



11 



56r'E 



in. 



IH 



u 



15f 



li 



