Haichkr : SKKi.F.roN or TrrANOTHKRiUM Disi'AK ;;.").■? 



in the type skeleton of T. robitstiiin this region of the tail is complete 

 and shows conclusively that it is the third and not the second which 

 bears the large chevron. 



The different degrees of distortion, due to the various positions of 

 the several bones as they lay imbedded in the matrix, were both inter- 

 esting and instructive, showing in some cases to what very great pres- 

 sure they had been subjected and in others how the general form and 

 proportions of a bone may be altered by slow and extreme pressure 

 without leaving upon its external surface more than faint indications of 

 such changes. As an example of the first instance I may cite the 

 femora shown in Figs, i, 2, 3, 4, plate XVI., which represent the 

 right and left femora of our skeleton. As stated above the former of 

 these stood upright in the beds and received the force exerted by the 

 pressure of the superincumbent strata in a direction parallel with its 

 longer axis, while the left femur lay in a horizontal position and the 

 same pressure was directed at right angles to its longer axis, directly 

 opposite conditions to those affecting the right femur, so that the 

 tendency was to shorten the right femur with little or no change in 

 its cross-section, while the left femur was slightly lengthened and con- 

 siderably flattened. The difference in length thus produced in these 

 two femora from opj^osite sides of the same individual are well shown 

 in the photographs reproduced in plate XVI. Figs, i and 2 show 

 respectively the right and left femora as they appeared when unpacked 

 in the museum laboratory, still covered with strips of gunnysacking 

 saturated with flour paste and applied in such manner as to hold each 

 fragment in its proper position. Figs. 3 and 4 show the same bone- 

 with the covering removed, the left with the different pieces carefully 

 cleaned and cemented together, while those forming the right are 

 fitted together but not cemented. As will be seen by these photo- 

 graphs the right femur was some six inches shorter than the left, and 

 this difference in length may be taken as a very fair estimate of the 

 vertical compression of the clays containing them due to the expulsion 

 of the acjueous material and the rearrangement of the particles com- 

 posing the clays brought about by the enormous pressure exerted by 

 the superincumbent strata accumulated long subsequent to the deposi- 

 tion of the beds containing the bones, and which at this locality must 

 have had a vertical thickness of more than 1,000 feet. 



The humeri occupied relatively the same positions as the femora 

 except that in this case it was the left that stood upright while the 



