HATCHER: OSTEOLOGY OF HAPLOCANTHOSAURUS 35 
doubt but that the number of presacrals in the present genus exceeded that of the 
same series in Diplodocus. 
The Sacrals. (Figs. 15, 16 and 20.) 
The sacrum of the present skeleton differs considerably from that of the type of 
Hf. priscus. Its position in the quarry is shown in the diagram at Sa. Only the 
neural spines and diapophyses, the parapophyses of the right side and the centra of 
the fourth and fifth sacrals are preserved. ‘The neural spines of the first, second, 
third and fourth sacrals are confluent and firmly codssified throughout their entire 
length, while the spine of the fifth is coossified only at the top and the bottom 
with that of the fourth sacral, and medially there is an elongated foramen between 
these spines shown at fin fig. 15. The spines of the two anterior sacrals rise nearly 
perpendicular, those of the third and fourth are directed somewhat backward, while 
that of the fifth is again directed forward to meet at the apex that of the fourth 
sacral. The spines of the first, second, third and fourth sacrals bear diapophysial 
laminee, and at the summit these expand into prominent rugosities. 
The diapophyses of the first and second sacrals are directed outward, forward and 
a little upward, nearly parallel to one another. Those of the succeeding sacrals are 
directed outward, backward and a little upward, parallel to one another, but that 
of the third meets that of the second in an acute angle at the base of the diapophy- 
sial lamina, forming a letter V with the apex directed toward the spine. The dia- 
pophysis of the third sacral is formed by the union of branches from the diapophysial 
laminee of the second and third sacral spines. 
All the parapophyses (sacral ribs) of the right side are present and nearly com- 
plete. They all show sutural surfaces for articulation with the sacral centra and 
with the iium. The parapophyses are shown in position in the view of the sacrum 
from the right side seen in Fig. 15, while comparative front views of the individual 
parapophyses are given in Fig. 16, a, b, c, d, é, which represents the series from the 
first to the fifth, respectively. Of the five parapophyses the first is the more slender. 
It is triangular in outline, with an emarginate base describing a nearly complete semi- 
circle. It may be described as composed of a horizontal and ascending branch. The 
surface for contact with the centrum is not greatly expanded. There are two sur- 
faces for contact with the ilium, one inferior, the other superior and separated by a 
distance of about 215 mm. The inferior of these surfaces is more pronounced and 
both show prominent rugosities. The anterior surface of this bone is convex, the 
posterior concave. Between the inferior and superior surfaces for contact with the 
ilium there was an elongated foramen enclosed externally by the ilium and in- 
ternally by the ascending branch. 
