52 
backward to its highest point, where it is strongly united with the nasals 
by interlapping finger-like processes, much as in Cheneosaurus. A short 
distance in advance of the anterior end of the jugal a broad, shallow groove 
runs obliquely upward and slightly backward across the lower part of 
the premaxillary, as in Lambeosaurus and Corythosaurus. 
The crest above and in front of the orbits is swollen outwardly on both 
sides and this swelling undoubtedly indicates the extent of the enclosed 
chamber, which has been so fully described 1 by Lambe in a skull of Lam- 
beosaurus. This part of the crest has a greatest transverse diameter 
near the base of 153 mm., whereas directly above, near the 
apex, it is only 13 mm, in thickness. Viewed from the front the 
facial slope is relatively broad transversely, and strongly convex in the 
same diameter except for a median longitudinal depression that rapidly 
fades out as the beak proper is approached. 
The narial passages are completely roofed over, and the anterior nares 
thus occupy an advanced position as in Cheneosaurus. Anteriorly the 
premaxillaries are broadly and somewhat angularly expanded to form the 
characteristic duck-like bill. They are excavated in front by wide V-shaped 
narial depressions, floored throughout by bone, and with a complete inter- 
narial septum. The structure of this septum is beautifully shown in a 
cross-section made by C. M. Sternberg, at a natural break 10^ inches 
from the anterior extremity of the beak. This section (Figure 14) shows 
that the median septum, though very thin, is made up of two walls 
separated at the centre by the median premaxillary suture. A second 
cross-section (Figure 15) from a second skull, at a slightly more advanced 
position through the external nares, shows that the septa and the other 
walls rapidly thicken toward the front. The under side of the anterior 
ends of the premaxillaries have low, pseudo tooth-like projections that in 
life were doubtless covered by a horny skin. 
The prefrontal, shown best on the left side of the skull, is roughly 
triangular and forms the upper boundary of the orbit. It was apparently 
in contact with the lachrymal, but one cannot be positive of this fact due 
to the damaged condition of this region in both skulls. 
*Op. cit,, pp. 74, 75. 
i 
