AET. 18 ON A NEW SKELETON OF DIPLODOCUS GILMORE 19 



Table 5. — Measiirements of pelvic bones of Diplodocus 



RIeasurement 



Greatest length of ilium - 



Greatest width of pelvis across the posterior end. 

 Greatest depth of ilium through greater peduncle 



Greatest width of acetabulum 



Greatest width of centrum of fifth sacral 



Greatest length of pubes --. 



Greatest breadth of proximal end 



Greatest length of ischium 



Greatest breadth of proximal end 



U.S.N.M. 

 No. 10865 



Mm 



945 

 920 

 635 

 380 

 384 

 820 

 410 

 870 

 515 



CM. No. 

 84 



Mm 

 1,089 



1,000 

 400 

 940 

 436 



Fore limb. — The preservation of both humeri, the ulnae, and the 

 right radius with this specimen makes these, so far as I can learn, 

 the most complete fore limbs yet found in definite association with 

 so complete a skeleton of Diplodocus. Furthermore, the right limb 

 was found articulated at the elbow, and it gave proof of the correct- 

 ness of Hatcher's observations " as to the proper articulation of these 

 bones at this joint. Reference is especially made to the position of 

 the proximal end of the ulna, which almost entirely incloses the 

 radius and has its articular surface opposed to that of the humerus 

 throughout its entire breadth. The radius articulates with the 

 median anterior surface of the humerus only. 



The most striking feature of the Diplodocus humerus is the strong 

 angulation of the two ends in relation to each other. In other words, 

 planes passed through their greatest diameters would bisect one an- 

 other at an angle of 45°. When placed in position in the articulated 

 limb this torque throws the deltoid crest far in under the main axis 

 of the bone. The head is situated in about the middle of the proxi- 

 mal end and is not produced backward beyond the posterior border. 

 At the distal end the ulnar and radial condyles are feebly developed 

 in front and separated by a longitudinal groove. The anconeal fossa 

 is moderate in depth. 



The radius and ulna have been illustrated and described by 

 Hatcher -^ so that it is needless to mention them further here. 



The restriction of the articular surface of the two extremities of 

 the humerus entirely to the ends and the almost total absence of an 

 olecranon process on the ulna are both features indicating that the 

 limb was not greatly flexed at the elbow in a standing position, a fact 

 that is quite in keeping with the great weight to which they gave 

 support. These features are in striking contrast to the robust 

 olecranon and extensive articular surface of the humerus in such 

 strongly flexed limbs as are found in Stegosaut'us and Triceratops. 



^- Mem. Carnegie Mus., vol. 2, no. 1, pp. 72, 73, 1903. 

 =»Loc. cit. pp. 72-73. 



