HATCHER: OSTEOLOGY OF HAPLOCANTHOSAURUS 23 
above middle of inferior border of centra in presacrals and above inferior border 
of posterior end in postsacrals. 
The inconsistencies that appear in the above table of measurements are due to 
the varying amount of crushing to which the different vertebrae were subjected 
while entombed in the sandstones. In this connection it should be remembered 
that these animals lived in a period long previous to that which witnessed the final 
upheaval of the front range of the Rocky Mountains and that the bones, as well as 
the sandstones in which they were imbedded, have been subjected to the enormous 
pressure which effected the upheaval of that mountain range. Little wonder that 
they are in many instances much crushed and distorted. It thus happens that the 
measurements given above are of value only as giving a general idea as to the sev- 
eral dimensions of the various vertebrae. In most instances they cannot be consid- 
ered as representative of the exact measurements and therefore capable of being 
compared critically with those of other skeletons. 
The Chevrons (Figs. 7, 8, 9, 10). — Only two chevrons were found. One of these 
(Figs. 7 and 8) was found in position between the eighth and ninth caudals. It 
does not differ materially from the chevron of the 
same region in Diplodocus or Brontosawrus. It is Y- 
shaped with the open portion somewhat abbreviated 
and the inferior portion elongated, compressed and 
with spatulate extremity. The articular surfaces of 
opposite sides at the proximal ends are not confluent. 
The length of this chevron is 313 mm. When seen 
to) 
from the side, it curves less strongly backward at the Fries. 7 and 8, chevron between 
: : ; caudals 8 and 9, side and posterior 
distal end than does the same chevron in Diplodocus.- _. ss 
views respectively, one-tenth nat- 
The other chevron (Figs. 9 and 10) was found in  ypya) size. 
position articulating with caudals thirteen and four- Fics. 9 and 10, chevron between 
feen. It differs from the one just described in its Ccavdalstéand 14 jside‘and posterior 
smaller size and in the more elongated open portion fC ee eee 
of the Y as compared with the closed inferior portion. avi 
At the point where the two branches meet it is greatly constricted antero-posteriorly, 
while distally it is much expanded in the same direction, but without the anterior and 
posterior projections which are already quite prominent in the same and the preced- 
ing chevron in Diplodocus. This chevron has a length of 184 mm. 
The Ribs (Figs. 11, 12 and 13).—The ribs do not differ essentially from those of 
other members of the Sauropoda. They increase in length and strength quite rap- 
idly from the first to the fourth when they continue subequal in length until in 
