58 
Measurements of Dentary and Teeth 
Mm. 
Greatest length of ramus as preserved 530+ 
“ length of dentary 465 
“ depth of dentary at centre to alveoli 08 
“ height of coronoid process 231 
“ depth of dental magazine at centre 102 
“ length of dental magazine 290 
Average length of nonfunctional teeth 37 to 38 
“ width of nonfunctional teeth at centre 11 
Total number of vertical rows of teeth 40 
Vertebrce 
The vertebral column of specimen No. 8501, according to notes made- 
in the field at the time of collecting, consists of an articulated series begin- 
ning in the anterior dorsal region and continuing backward well down (11 
feet) into the tail. At this time only two partly prepared sections are 
available. A large block showing the right side contains the preacetabular 
portions of the right ilium and pubis, ten or more dorsal vertebrae in sequence, 
and their respective ribs. All these bones have been but little disturbed, 
and apparently occupy their natural positions in relation to one another. 
The spinous processes protruded from the rock, and although several 
of them are nearly complete, only one has its upper extremity fully intact. 
It is regarded as the fourth dorsal in front of the sacrum, reckoning from 
its position in relation to the ilium as compared with known articulated 
hadrosaurian skeletons. This vertebra has a greatest height over all of 
about 602 mm., a greatest diameter antero-posteriorly of the centrum of 
about 95 mm., an estimated vertical height of the centrum of about 110 
mm. These proportions show a relatively shorter spinous process than in 
any of the vertebrae of this region of the type of associated specimens 
described by Brown, although it comes within his published proportions of 
the vertebrae. 
In establishing the genus Hypacrosaurus, Brown has laid much empha- 
sis on the great height of the spines, which are said to be from five to seven 
times the height of their respective centra. Though the single complete 
vertebra available for measurement falls within these proportions, the 
evidently somewhat greater length of the vertebrae immediately preceding 
the fourth presacral will bring them within the given proportions, although 
it is believed none would reach the maximum height of the typical specimens 
of Hypacrosaurus altispinus. 
The spines of the dorsal series are not only high, but are massive, 
long antero-posteriorly, and thick. It is apparent that those from the 
middle of the dorsal series are largest. The eighth and ninth vertebrae 
in front of the sacrum show a decrease in antero-posterior width of the 
spines as in the genotype. The upper extremity of the fourth vertebra 
preceding the sacrum is expanded transversely with an obliquely truncated 
end that slopes toward the rear. In the posterior vertebrae the spines are 
inclined forward, but the eighth and ninth have a backward inclination. 
The sides of the centra, so far as they can be observed, are deeply 
concave antero-posteriorly. The neural arches are comparatively weak 
and deeply excavated behind the transverse processes. The median plate 
descending from the posterior zygapophyses is apparently intact, and 
