40 
the bone and which appears to be comparable with the so-called infraorbital 
foramen in the Ceratopsia. 1 The distance forward from the jugal articula- 
tion to the lower border of this foramen forms an important character for 
distinguishing the Lambeosaurinse from the other members of the Hadro- 
sauridse, inasmuch as the distance has been greatly shortened antero- 
posteriorly in all members of this sub-family, whereas it is relatively long 
in the Saurolophinse and Hadrosaurinae. The high external superior 
maxillary process mentioned above, passes up behind the jugal and is in 
contact with the lachrymal above. 
In the type specimen parts of the right pterygoid, and nearly 
complete ectopterygoid, and palatine bones remain articulated with the 
maxillary of that side. The ectopterygoid (Plate VII) has its greatest 
length in an antero-posterior direction. It is thin, except at the anterior 
end where it thickens outwardly to abut against the inner lower surface of 
the jugal. This bone is closely applied to the inner and posterior-superior 
surface of the maxillary, having a long contact internally with the 
pterygoid and a short but heavier articulation with the palatine. The 
fragment of the palatine present rests upon the superior-anterior end of 
the ectopterygoid, with the greatest diameter of this piece transverse. 
The outer end is strongly in contact by a roughened expanded surface 
with the jugal, and its inner border meets the forwardly directed process 
of the pterygoid. 
The pterygoid is seen to have the usual irregular form of this bone. 
It closely envelops the supero-internal and postero-internal surfaces of the 
ectopterygoid. A thin anteriorly directed process is in contact with the 
upper edge of the ectopterygoid and anteriorly with the fragmentary 
palatine. Posteriorly the pterygoid sends a broad, thin, nearly vertical 
wing-like process back to meet the quadrate. A shelf extending inward 
on the lower internal side makes its lower edge appear relatively wide. 
The occipital region in all the skulls is so poorly preserved as to con- 
tribute but little to our knowledge of its structure. The right paraoccipital 
process in the type has a very broad, expanded, hatchet-shaped outer 
extremity, that, on its anterior face, broadly rests against the squamosal. 
The outer end is especially produced in a ventral direction ending in a 
flattened obtuse process that hangs far below the posterior process of the 
squamosal. This end of the paraoccipital has a greatest vertical diameter 
of 122 mm. 
“Anteriorly the premaxilla is somewhat depressed, but laterally 
much expanded. Its upper surface, next to the median line of the head, is 
continued in a curve outward anteriorly and backward laterally as a 
marginal area enclosing a wide depression in advance of the long and 
narrow nasal opening.” In the Lambeosaurinse the external nares and 
nasal passages of the two sides are separated by the premaxillaries, the 
latter being enclosed outwardly by an upward growth of the floor of the 
passage and a downward bend of the roof of the same. 
“In Stephanosaurus [Lambeosaurus] the nasal passages lead up into 
the front part of a large double chamber within the crest, the entry [appar- 
ently] being made at about the mid-height of the chamber on either side 
1 Mon. 49, U. S. Geol. Surv., 1907, if. Figs. 20, 21, and 22, pp. 26, 27. 
