36 MEMOIRS OF THE CARNEGIE MUSEUM 
In the parapophysis of the second sacral the horizontal branch has become very 
strong and much expanded at either extremity for contact with the centrum and 
ilium. The ascending branch is broad but very thin, and presents at its extremity 
only a small rugosity for contact with the ilium. The foramen between it and the 
ilium was broader than that separating the same branch of the preceding para- 
pophysis. Immediately above the surface for contact with the centrum there is a 
rugosity which doubtless gave support to the descending branch of the diapophysis, 
Fie. 15. Sacrum of Haplocanthosaurus utterbacki, seen from right side, ;'> natural size. a, anterior 
extremity ; p, posterior extremity ; 1, 2, 3, 4, 5, spines of first to fifth sacrals; f, foramen between spines 
of fourth and fifth sacrals. 
Fic. 16. Anterior view of disarticulated parapophyses (sacral ribs) of Haplocanthosaurus utterbacki, 
ip hatural size. a to e, first to fifth respectively ; y, surface for contact with sacral centrum ; 2, inferior 
surface for contact with ilium ; z, superior surface for contact with ilium. 
but it would appear that the diapophysis and parapophysis were not in contact 
throughout their entire length, but were separated for a considerable distance by an 
elongated foramen. ‘The external extremity of the horizontal branch is greatly 
expanded transversely so as to unite with the same element in the succeeding para- 
pophysis, to form the acetabular bar and give additional support to the ilium. 
The parapophysis of the third sacral differs from that just described in its shorter 
horizontal branch and narrower and more slender ascending branch. The shorten- 
