hatchee: diplodocus (marsh) 45- 



The Fore Limb and Foot. — Little is known of the fore limbs and feet of Diplodocus. 

 In our collection there are no bones that can positively be referred to these parts. 

 Marsh has figured a complete set of metacarpals which he refers to Diplodocus. 

 Through the kindness of Professor Osborn I am able to give the following brief de- 

 scription of the fore limbs as represented by material in the collections of the Amer- 

 ican Museum, photographs of which have been placed at my disposal. These show 

 that the fore limbs had a length of about three fourths of that of the hind limbs. 

 The humerus Avas rather slender, somewhat compressed antero-posteriorly, and with 

 a prominent deltoid ridge. Distally the radial articulation was external and an- 

 terior to the ulnar, so that these bones were crossed superiorly as in the mammalia. 

 The bones of the forearm were rather long and slender, but somewhat shorter than 

 the tibia and fibula, while the metacarpals were longer than the metatarsals and ac- 

 cording to Osborn the carpus was of the mesaxonic pattern and digitigrade. 



Tlie Pelvis. — The pelvis of Diplodocus is composed of ilium, ischium, and pubis. 

 These all unite to form the acetabulum, Avhich is left open internally. They are not 

 coossified. The superior border or crest of the ilium is semicircular in outline, and 

 is much thickened and rugose. Below this the ilium is quite thin, but along the 

 inferior border it is again thickened and about the acetabulum it attains a thickness 

 of from six to eight inches. There are anterior and posterior expansions of the iliac 

 crest. The former of these is much the longer. Inferiorly the acetabular border of 

 the ilium is produced into a short posterior ischiac peduncle and a very long and 

 stout anterior pubic peduncle. The latter was almost perpendicular when the 

 animal was in its normal quadrupedal position, but when the bipedal or tripodal posi- 

 tion was assumed its position became more horizontal and it thus received a cor- 

 respondingly increased proportion of the weight of the elevated anterior portion of 

 the body. The pubes are broad and stout proximally and much thickened about 

 the acetabular border. The face for articulation with the ischium is broad and tri- 

 angular. Inferiorly the pubis is produced into a rather long shaft terminating in 

 an expanded club-like tuberosity with a broad internal rugose surface for contact 

 with the corresponding portion of the opposite pubis. The shaft is very thin and 

 sharp along its internal margin and much thickened and rounded externally. There 

 is a prominent rugosity on the anterior portion of the pubis just below the articular 

 surface for the ilium. The articular surface for the ilium is concave in all our pubes. 

 There is a very large foramen just within the ischiac border. The broadly expanded 

 proximal ends of the pubes are concave internally and convex externally. The 

 ischia are the smallest of the pelvic bones. They are much expanded proximally, 

 contracted medially, and slightly expanded distally. The shaft is trihedral in cross 



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