69 
as expressed in his ‘‘Geology and palaeontology of the Judith River beds,” 
1905, p. 97J This author in the writer’s opinion also erred in his remarks^, 
under the same heading in his report, on the material on which S. mar- 
ginatus was established, as further work on the rich dinosaurian fauna 
of the Belly River beds of Alberta has so fully proved. 
The members of the Hadrosaurince and Saurolophinoe resemble each 
other in having an elongated narial vacuity, opening through the skull, 
enclosed above by the nasals and premaxillaries. In both subfamilies 
there is a forward extension of the nasals, and a limitation of the pre- 
maxillaries to an anterior position in the skull. They differ from each 
other in the absence in the first and the presence in the other of a “foot” 
or distal expansion in the ischium. 
The three subfamilies show distinctive characters in the relative 
size of the parieto-frontal region, and of the lachrymal. 
The Stephanosaurince are characterized by an extremely high skull 
in marked contrast to the relatively low skull of the Hadrosaurince and 
Saurolophinoe, the extreme of skull depression being reached in the Hadro- 
saurince, viz., in the genus Diclonius. The primary characters of the 
Stephanosaurince separating it from the other two are — (1) the envelopment 
of the anterior nares in, and their separation by, the premaxillaries, (2) the 
extreme backward extension of the premaxillaries and their enclosure of 
the narial passages, (3) the enlargement of each narial passage posteriorly, 
within the supraorbital hood or dome, into an extensive air-chamber 
bounded by the premaxillaries and nasals. 
In these subfamilies the appendicular skeleton and that of the trunk 
provide also characters which no doubt can be relied on as being distinctive 
in each. 
The Stephanosaurince were more highly specialized than either the 
Hadrosaurince or the Saurolophinoe. The arrangement of the elements 
enclosing the anterior nares and narial passages implies different habits 
and may indicate a better adaptation to an aquatic life. 
The earliest member of the Hadrosaurince is Gryposaurus from the 
Belly River formation of Alberta represented in Figure 36A by the skull 
of G. notabilis remarkable for its completeness and wonderful state of 
preservation. 
The second genus of this subfamily, viz., Kritosaurus, from a not 
definitely determined geological horizon in New Mexico (the Ojo Alamo 
beds of San Juan county = ?Edmonton formation of Alberta) is note- 
worthy for the great posterior height of the skull. The radical differences 
between Gryposaurus and Kritosaurus, particularly those conspicuously 
seen in the shape and size of the predentary and the proportionate length 
of the quadrate, make it probable that further fundamental dissimilarities 
will be revealed in the skull and other parts of the skeleton when the 
osteology of Kritosaurus is better known. 
The type of Kritosaurus consists in general terms of the hinder half 
of the cranium, and a complete mandible, which latter reveals the length 
of the skull (Figure 36B). The orbital rim, including the postorbital' 
bar, is, in the mounted skull, mostly restored in plaster, and all the facial 
^“Geology and palseontology of the Judith River beds”, by T. W. Stanton and J. B. Hatcher, with a chapter 
on the fossil plants by F. H. Knowlton; Bull. No. 257, U.S. Geol. Surv. 
2Cited by C. F. Bowen in “The stratigraphy of the Montana group, with special reference to the position and 
age of the Judith River formation in north-central Montana”, Prof. Paper 99, U.S. Geol. Surv., 1914. 
