HATCHER: OSTEOLOGY OF HAPLOCANTHOSAURUS 13 
when discovered in the quarry near Canyon City, Colorado, were all closely inter- 
locked by their zygapophyses. They were taken up in a single block of matrix 
and were received at the museum still imbedded in the sandstone and in their 
exact original position relative to one another. Thus whatever question there may 
be regarding their position relative to the last cervical, there can be absolutely no 
question regarding their position relative to each other, while the same can be said 
with only a little less certainty regarding their position in relation to the sacrum, 
for the supposed fourteenth or Jast of this series, although removed some ten feet 
from the sacrum, agrees very well in size with the first sacral and has the posterior 
extremity modified for articulation with that vertebra. There can be no reasonable 
doubt but that these dorsals and cervicals formed part of the same skeleton as that 
to which belonged the pelvis and caudals shown in Plates I1I., [V., V., and the femur 
shown in text Fig. 14. 
In the dorsals now under consideration, the centra are comparatively small, con- 
stricted medially, opisthoccelous throughout, though less decidedly so in the posterior 
region. They are subequal in length, with those of the posterior region a little 
shorter than those of the anterior. The pleurocentral cavities are deep and sub- 
equal in area. hey are all irregularly ovate in outline with the broader end di- 
rected anteriorly. The neural arches are high and the neural spines short and stout. 
There is a striking contrast in the proportionate length of the neural spines and 
height of the neural arches in the dorsals of Haplocanthosaurus when compared with 
those elements in the same vertebree of any other genus of Sauropod dinosaur known 
to the present writer. This contrast is especially noticeable in Diplodocus and Bron- 
fosawrus but is less marked in Morosaurus. The capitular facets are somewhat 
pedunculate and gradually assume a more elevated position in the anterior dorsals 
until the eighth is reached when they attain an elevation equal to that of the an- 
terior zygapophyses. In the eighth and succeeding dorsals their position remains 
constant. The transverse processes throughout the entire series of vertebrae now 
under consideration are subequal in length and are directed upward and outward 
at an angle of about forty-five degrees. The transverse processes of the posterior dor- 
sals are somewhat more slender than are those of the anterior dorsals. Commenc- 
ing with the eighth dorsal the superior blade of the diapophysial lamina becomes 
very well developed and in this and the succeeding vertebra it unites, about mid- 
way up the spine, with the superior blade of the postzygapophysial lamina to form 
a single lamina giving lateral support to the neural spine. The posterior position 
of the extremity of the transverse process in the eighth dorsal as shown in Plate I., 
Fig. 8, is due to distortion and is not the normal position of that element. In the 
c 
