24 MEMOIRS OF THE CARNEGIE MUSEUM 
about the region of the ninth or tenth. Posterior to these, they rapidly become 
shorter and more slender. ‘The ribs of the anterior and mid-dorsal region are much 
expanded proximally where they present a rather deep concavity on the posterior 
surface, while the anterior surface in the same region is convex. Beyond this they 
become subcircular in cross-section and somewhat spatulate at their distal extremi- 
ies. The ribs of the posterior region are decidedly less expanded proximally and 
in the middle they are semicircular in cross-section. 
Figs. 11, 12 and 13 represent respectively anterior views of the supposed 
second, fourth and thirteenth ribs. The second rib has a length of 911 mm., the 
Fic. 11. Anterior view of second? rib of right side, one-tenth nat. size. 
Fie. 12. Anterior view of fourth? rib of left side, one-tenth nat. size. 
Fie. 13. Anterior view of thirteenth? rib of left side, one-tenth nat. size. 
fourth 1,394 mm. and the thirteenth 710 mm. Compared with the size of the 
animal as a whole the ribs of Haplocanthosawrus are neither long nor robust. 
Throughout the entire series the capitulum and tuberculum are well separated. 
The capitulum is pediceled while the tuberculum is sessile, save in the anterior ribs 
where it is also pediceled. ; 
The Pelvis (Plates IV. and V.). 
All the elements of the pelvis were found approximately in position and in a 
splendid state of preservation. 
The Ilium (Plate IV., Fig. 3).—In general form the ilium resembles that of other 
members of the Sauropoda. In the present skeleton both ilia were found attached 
to the sacrum which lay imbedded in the sandstones with the spines directed up- 
wards but reclining a little on its right side. It thus happened that these elements 
received the pressure of the superincumbent rocks in a direction obliquely vertical 
and from the left. This pressure was sufficient to accomplish considerable crushing 
and the superior borders of the ilia have been considerably flattened and instead of — 
describing the are of a circle as was doubtless the case before this distortion took 
place, for a considerable distance along their superior borders they now present a 
