66 
maximum thickness proximally. Both ends are enlarged, the proximal one 
more than the distal one. In comparison with the ulna, the radius is 
more slender throughout, with less disparity in the size of the ends. At 
midheight the shaft has an elliptical outline in cross-section as in the 
ulna but smaller, the diameters in the two bones being in about the pro- 
portion of 4 to 5. The outline of the proximal end in superior aspect 
is nearly square with the greater diameter transverse and the outer and 
posterior sides fitting into the angular excavation of the ulna. The increase 
in the size of the proximal end is rapid on the inner and hinder faces, par- 
ticularly on the latter. Externo-anteriorly for some distance below the 
upper end the bone narrows outwardly forming a vertical ridge, most 
protrudent above, which is rugosely striated in the direction of its length 
and is in close contact, when the bone is in position, with the ulna. The 
lower end is angulated internally and thickens toward the outer side where 
it is applied to the ulna. On all sides it is longitudinally striated deeply 
for muscular attachment. Similar striations are conspicuous also at the 
upper end. 
Measurements of Left Radius of Paratype of Edmontosaurus. 
Mm. 
Length 665 
Maximum transverse breadth of proximal end 98 
Maximum diameter of distal end 87 
Maximiim diameter at midlength 65 
THE GENUS EDMONTOSAURUS, 
The orthopod genus Edmontosaurus of the family Hadrosauridse, 
subfamily Hadrosaurince (p. 68) represented by the single species E. 
regalis, Lambe, has the following characters : 
Generic and Specific Characters. Skull moderately elongate, high and 
broad posteriorly, fiat in the frontal region, laterally compressed behind 
a low, greatly expanded snout. Orbit large. A large pocket-like recess 
developed within the postfrontal, leading from the orbit. Lateral tem- 
poral fossa restricted above. Palatine and pter}^goid rising, at a high 
angle, inward. Ectopterygoid external to the maxillary and pterygoid, 
connecting the two. ^landible deep and strong, very slightly decurved 
in front. Teeth with a rounded apical outline in lateral aspect, keeled, 
and with smooth borders; in 48-49 vertical rows in the dentary, and 51-53 
in the maxillary. Ischium long, bluntly pointed distally. Femur slightly 
longer than the tibia. Humerus nearly as long as the ulna. Cervical 
and dorsal vertebra opisthoccelous, in a marked degree in the former. 
Dorsal spines of moderate size, increasing slightly in height backward in 
the series. Sacrum composed of eight vertebra. Animal of robust build, 
between 30 and 40 feet long. 
Edmontosaurus approaches most closely Diclonius Cope of later 
geological age, one of the principal characters distinguishing the two being 
found in the general shape of the skull which in Edmontosaurus is high and 
in Diclonius greatly depressed. The name Diclonius, as used here, is 
reserved for D. mirabilis, Cope, from the Lance formation of Dakota, 
sometimes referred to as Trachodon mirabilis a genus and species insecurely 
established by Leidy in 1856, on the tooth from the Judith River beds of 
