18 



PKOCEEDINGS OF THE NATIONAL MUSEUM 



VOL. 81 



haps the most radical departure from previously held views is that 

 of Osborn and Mook in a reconstruction of Gamarasaurus supreirvas 

 in which the shoulder blade is placed in a nearly vertical position 

 that brought about a great elevation of the shoulders, making this 

 the highest point in the vertebral column. The natural downward 

 curve of the anterior dorsal vertebrae in the present skeleton renders 

 this pose impossible in Diplodocus. There seems to be further ob- 

 jection on account of the fact that with the scapula in a nearly verti- 

 cal pose the coalesced coracoid has its lowermost extremity thrown 

 in so close to the front of the humerus as seriously to interfere with 

 its movement, whereas a more horizontal position at once relieves 

 this condition. 



In the present skeleton the scapula has been posed in a more 

 inclined position for the reason that the anterior ribs have flattened 

 external surfaces that seem adapted to the purpose of providing a 

 surface over which the elongated blade of the scapula could play. 

 Furthermore, an articulated skeleton of Camarasam^us lentus ^^ in the 

 Carnegie Museum gives first-hand evidence that the scapula in saur- 

 opodous dinosaurs occupied a more horizontal position. In this con- 

 nection it is of interest to note that Prof. R. S. Lull has reached 

 the same conclusion as illustrated by the skeleton of Gamarasaurus 

 lentus and Brontosaurus excelsus recently mounted under his direc- 

 tion.2« 



Table 4. — Comparative measurements of scapula and coracoid of Diplodocus 



Measurement 



CM. No. 

 84 



Combined length of scapula and coracoid 



Greatest length of scapula 



Greatest breadth of scapula 



Least breadth of scapula 



Length of coracoid 



Greatest expanse of glenoid cavity 



Pelvis. — The complete pelvic arch was recovered. The ilia 

 were found attached to the sacrum, but the pubes and ischia, though 

 each pair remains articulated, had been shifted to the eastward of 

 the main part of the skeleton. These bones are in full accord with 

 Hatcher's description of the pelvis of Diplodocus and call for no 

 special comment here. Their principal dimensions are given in 

 Table 5. 



^ Gilmore, C. W., Mem. Carnegie Mus., vol. 10, p. 376, plB. 14, 17, 1925. 

 «Amer. Journ. Sci., vol. 19, p. 3, fig. 1, 1930. 



