60 
The pubis is comparatively short with broadly expanded thin blade. 
So far as it has been observed it appears indistinguishable from the pubis 
of Saurolophus as figured by Brown 1 . 
The most distinctive feature of the pelvis is found in the long, massive 
ischium, having a closed foramen and a heavy expanded foot. It unites 
with its fellow of the opposite side along the inner distal third of the shaft 
by a flattened longitudinally striated surface. The foot-like expanded 
distal ends of the united ischia closely resemble the pubic foot found in 
many of the theropodous dinosaurs. In the presence of a closed foramen 
and the extent and straightness of the anterior border of the proximal end, 
this bone resembles the ischium of Saurolophus osborni much more closely 
than it does the ischium pertaining to the type of Hypacrosaurus altispinus 
Brown, with a notch and much shorter ventral border. In all other respects, 
however, these two bones are remarkably similar. 
A re-examination of the type ischium of H. altispinus by Matthew, 
as explained on page 49, shows that in all probability it also had a closed 
foramen and that if perfectly preserved, the differences noted above would 
largely disappear, as shown in Figure 17. 
Hind Limb and Foot 
The bones of the hind limb and foot are all present and excellently 
preserved. All are free from distortion except metatarsal IV, which 
suffered an injury in life that developed a pathologic condition which has 
deformed and destroyed the natural contours of its shaft and distal end. 
The femur is heavy and massive, with a long straight shaft. It is 
124 mm., or nearly 5 inches longer than the tibia. Brown, however, 
observes 2 “this genus differs somewhat from the usual form in other genera, 
especially in the more equal length of femur and tibia, also in the greatly 
lengthened metatarsals.” I have gone over all available hadrosaurian 
specimens, and especially published measurements, and find that the 
proportions of these bones are remarkably similar in all. It would thus 
appear that this difference in length between the femur and tibia is not 
<listinctive of the genus Hypacrosaurus, for although Brown does* * not 
publish the measurement of the femur he illustrates the hind limb (Figure 7) 
and the proportions given are almost identical with the specimen now 
before me. 
On the distal end of the femur the condyles are strongly developed 
antero-posteriorly and on the anterior face completely enclose the large 
foramen. The lesser trochanter is separated by a narrow cleft, and ends 
considerably below the greater trochanter, which rises higher than the 
head. The fourth trochanter is strongly developed as a transversely 
flattened triangular process that projects almost straight backward from 
the posterior internal surface of the shaft. The apex at its greatest width 
lies almost directly in the midlength of the bone. 
The tibia is also heavy in its construction, with a very strong enemial 
crest and well-developed condyles. The proximal end has a greatest 
diameter antero-posteriorly of 320 mm., and a greatest transverse diameter 
‘Bull. Am. Mus. of Nat. Hist., vol. 32, 1913, p. 390, Figure I. 
*Op. cit., p. 405. 
