59 
not perforated from side to side as in the type. The transverse processes 
are relatively small and incline decidedly upward and backward in those 
few vertebrae in which they can be observed. 
The sacrum has not been prepared, but the field notes say it consists 
of eight vertebrae, as in the type of H, aitispinus. 
A block containing a series of anterior caudal vertebrae, beginning 
with the first or second back of the sacrum, shows these vertebrae to be 
very similar to those described by Brown, but slightly smaller. The 
centrum of the first is large, the width equalling twice the length. The 
anterior end is decidedly concave vertically. The sides are concave 
antero-posteriorly. Spines are high and strongly inclined backward. 
The transverse process of the first is large and connected with the spine by a 
high, thin plate; in the following ones, however, this plate has disappeared, 
and they become simple horizontal bars projecting straight outward from 
their respective centra. For a short distance backward of the first in this 
series they increase in length, and then again become successively short- 
ened as they proceed distally. 
The inability at this time, from lack of preparation, to properly study 
the vertebral column of this specimen renders it exceedingly difficult to 
make precise comparisons. However, the very great development of the 
spinous processes of the middle and posterior dorsal region leaves but little 
uncertainty that the proper reference of this specimen is to the genus 
Hypacrosaurus, None of the other known hadrosaurs from the Edmonton 
formation approach Hypacrosaurus in this respect, and if the final study 
should disclose differences that are not now apparent, it can safely be 
predicted that a new genus would need to be created rather than there 
being a possibility of it falling within any of those now established. 
Fore Limb 
The distal two-thirds of the humerus, and the radius and ulna of the 
right side show the fore limb to have the same relative proportions as 
found in the other crested hadrosaurs, the radius being much longer than 
the humerus, as in the paratype described by Brown. The humerus is 
short and heavy, whereas the limb bones of the fore arm are slenderly 
elongated. The field measurement for the complete humerus is 19 inches 
(482 mm.), though by comparison with the paratype it appears to be 
slightly in excess of that measurement. The radial crest is strongly 
developed. 
Pelvis 
The pelvis is represented by the right ilium, right pubis, and both 
ischia. All of these are about subequal in size with the pelvic bones of 
the type of Hypacrosaurus aitispinus. 
The ilium is sufficiently well preserved to show that the preacetabular 
portion was strongly decurved, as it is in all of the crested Hadrosaurs. 
It differs from Corythosaurus in being deeper, and from Thespesius annec- 
tens (Marsh) in having a shorter, and transversely thin preacetabular 
process as contrasted with the elongate, triangular, slightly decurved 
extension in that species. It has the usual heavy process overhanging 
the ischiac peduncle. 
