the Skeleton of Diplodocus Camegiei. 



361 



With regard to skulls of Diplodocus, Marsh had only two. The 

 Carnegie Museum has a skull, but no complete skull is vet known. 

 We have to be .content with the photographs, etc., in the paper by 

 Dr. W. J. Holland already referred to. The restored skull in the 

 reconstructed skeleton in the Natural History Museum is based on 

 these two skulls, but it probably will be modified when other 

 specimens are discovered. The vertebral formula seems to be : — 

 Cervicals 15, dorsals 11, sacrals 4 (or 5), caudals 35 (or 34). 



The Posterior Limbs. 

 We must pass on now to consider the hind-limbs. Let us take, for 

 example, the elephant, and see how its limbs work, comparing it 

 with a lizard, such as Varanus. In Elephas the femur works up 

 and down in a plane practically parallel with the axis of the body. 

 In consequence a clear space is left for it by the late dorsal ribs, for 

 they rapidly get shorter about midway in the region between the 

 pectoral and the pelvic girdles. Also this enables the elephant to 

 sit down with its hind-limbs tucked away as a horse does. Now 

 Diplodocus could not have done this. Fig. 3 (p. 362) shows the 



FlG. 2. — Posterior aspect of the pelvis and hind-limb of Diplodocus (after 



Tornier). 



position of the hind-limb proposed by the writer. In the case of 

 Varanus, a lizard, we perceive something quite different ; there is not 

 the same clear space for the movements of the femur, for the obvious 

 reason that the femur of the reptile, instead of working up and down 

 in nearly a vertical plane, works in a plane more or less horizontal, 

 which may be compared to the movements of an oar in a rowing boat, 

 while the others might be compared to a pendulum, which swings in 

 a vertical plane. The ribs are shortened only when quite near to 

 the pelvic girdle. The proximal portion of the Diplodocus hind-limb 

 evidently was massive, to say the least, and the writer in his 

 restoration (Plate XXIII) has made it fairly big. It may therefore 

 well be asked how can room be found for this mass of flesh attached to 

 the femur and ilium except by putting the limb at an angle with 



