17 
The nasal bones are long and slender, their attenuated extremities 
embracing the slender posteriorly directed premaxillary processes. The 
premaxillaries form the whole of the anterior portion of the skull and are 
united at the centre by suture. They are deeply excavated for the nasal 
openings. The front borders of the anterior expansion of the premax- 
illaries is recurved for some distance so as to roof over the cavity, which 
opens backward. This bone appears to be somewhat thickened as con- 
trasted with the thin bone of this region of Edmontosaurus. On the left 
side the expanded beak has been distorted and flattened by crushing, but 
the right side appears to show the full normal width. 
The lower mandible is long, with a massive predentary, and is closely 
articulated with the skull from which it has apparently never been 
separated. For this reason the character of the tooth structure cannot be 
observed, and I am also at a loss to understand how Lambe was able to 
compare it with Trachodon marginatus in making his first identification 
of this specimen. 
A careful study and comparison of the skull of No. 8399 have revealed 
no differences in structure which might be considered of specific importance 
to separate it from T. annectens (Marsh) and were only the skull present, 
I should unhesitatingly refer it to that species. 
Measurements of Skull and Lower Jaws 
Mm. 
Greatest length, tip of beak to back of paraoccipital process 938 
Greatest length paraoccipital process to posterior (centre) border of orbit 246 
Greatest length anterior border of orbit to tip of premaxillary 554 
Greatest vertical diameter of Bkull and lower jaws 410 
Greatest vertical diameter of skull at muzzle. 250 
Greatest length of skull in front of teeth 310 
Greatest width of skull between centre of orbits 139 
Greatest width of skull across tops of quadrates 131 
Greatest width nasal and premaxillaries above centre of narial orifice 42 
Greatest width across expanded beak about 200 
Greatest length of quadrate 340 
Greatest height of orbit, taken obliquely 210 
Greatest length of orbit, taken at midheight 145 
Greatest height of infratemporal fossa, taken obliquely 227 
Greatest length of supra temporal fossa. 154 
Greatest width of supratemporal fossa 40 
Greatest length of nasal orifice : 280 
Greatest length of nasal opening 221 
Greatest length of ramus to front of articulated quadrate 695 
Greatest vertical diameter of ramus through centre of dentition 126 
Greatest length from tip of predentary to front border of coronoid process 530 
Vertebrae 
The complete articulated presacral series is present and consists of 
thirty-two vertebrae. The twelve anterior ones are regarded as cervical, 
the remaining twenty as dorsal. The sacrum is composed of nine coossified 
sacral vertebrae, as in all known members of the Hadrosaurinae. Only 
five anterior caudal vertebrae remain articulated with the sacrum, the others 
having been eroded away and destroyed before the specimen was discovered. 
The vertebral formula, so far as known, is C. 12, D. 20, S. 9, C. 5+. 
An examination of the compiled table, giving the vertebral formulae 
of various members of the Hadrosauridae, shows there is a considerable 
variation not only in the number of cervical and dorsal vertebrae, but also 
