THE POSE AND LOCOMOTION OF DIPLODOCUS 7 



sessed. Doubtless the Sauropodaand the Theropoda started out with 

 the same pedal outfit, and there seems to be no reason for supposing 

 that the former passed through an arboreal stage and back into an 

 ambulatory stage. 



The position of the trochanter major of the sauropods is open to 

 question and there are differences of opinion. Marsh* regards as this 

 trochanter the outer upper angle of the femur, including a part of 

 the rough surface forming the proximal end of the bone. Hatcher's 

 view (Mem. Carnegie Mus., I. p. 46) appears to be the same. Osborn* 

 has identified as the trochanter the rough surface which descends for 

 some distance below the upper end of the femur on the fibular border. 

 Neither of these views seems to the writer satisfactory. If the femora 

 of the Triassic dinosaurs described by v. Huene in his monograph, 

 Die Dinosaurier der europdischen Triasformation, be examined it 

 will be found that the trochanter in question is placed at a considerable 

 distance below the head of the bone, on the dorsal surface, and near 

 the fibular border. In the more highly specialized dinosaurs of the 

 Jurassic the trochanter is a distinct process arising from the position 

 described and ascending nearly to the level of the head. In such 

 dinosaurs as Trachodon and Triceratops the trochanter has reached 

 the outer upper angle of the femur, and is well separated from the 

 head by a distinct neck. The writer believes that in the sauropods 

 the trochanter occupied the same primitive position that it has in the 

 Triassic Theropoda. It is not essential that it should be represented 

 by a process or even by any unusual roughness, as is shown by the 

 femur of the crocodile. 



This being the case, what explanation is to be made of the outer 

 portion of the rough surface on the proximal end of the femur ? The 

 writer believes that it forms a part of the head of the bone and entered 

 into the acetabulum. The matter will be discussed. In order to 

 illustrate a possible position of the femur in the acetabulum a figure 

 is here presented (Fig. 2). This has been obtained by placing a 

 section of the proximal end of the femur, taken from Hatcher's figure 

 in Memoirs of the Carnegie Museum, vol. I, p. 46, in the acetabulum 

 as shown in the same writer's figure in the second volume of the same 



" Dinosaurs N. A., PI. XVI, fig. 3, t. 



•Mem. Amer. Mus. Nat. Hist., i, p. 211, fig. 14. 



