68 
Hadrosauridoe. 
Subfamily 
Saurolophince 
Subfamily 
Hadrosaurince 
Forms large. 
Posterior height of skull 
variable. 
Supraorbital region flat. 
Fronto-parietal area en- 
larged. 
Nasals extending far forward. 
Anterior nares transversely 
confluent. 
Nasal passages anteriorly 
not enclosed in bone. 
Premaxillaries confined to an 
anterior position. 
Lachrymal of moderate size. 
Ischium pointed distally. 
Genera: 
Gryposaurus. Belly River 
formation. 
Kritosaurus. Ojo Alamo 
beds of New Mexico = 
f Edmonton formation. 
Edmontosaurus. Edmonton 
formation. 
“Claosaurus^\ Lance for- 
mation. 
Diclonius. Lance forma- 
tion. 
Forms large. 
Skull high posteriorly. 
Supraorbital crest develop- 
ed. 
Fronto-parietal area moder- 
ately large. 
Nasals extending far for- 
ward. 
Anterior nares transversely 
confluent. 
Nasal passages anteriorly 
not enclosed in bone. 
Premaxillaries confined to 
an anterior position. 
Lachrymal large. 
Ischium expanded distally. 
Genera: 
Prosaurolophus. Belly 
River formation. 
Saurolophus. Edmonton 
formation. 
Subfamily 
Stephanosaurince 
Forms of variable size. 
Skull high: relatively short. 
Supraorbital region elevated 
into hood, or dome. 
Fronto-. parietal area reduc- 
ed. 
Nasals receded. 
Anterior nares separated by 
premaxillaries. 
Nasal passages enclosed by 
premaxillaries, and greatly 
enlarged in supraorbital 
region. 
Premaxillaries prolonged 
backward and entering 
largely into formation of 
hood or dome. 
Lachrymal reduced.* 
Ischium expanded distally. 
Genera: 
Stephanosaurus. Belly 
River formation. 
Corythosaurus. Belly River 
formation. 
Cheneosaurus. Edmonton 
formation. 
fHypacrosaurus. Edmon- 
ton formation. 
From the above comparison of the subfamilies of the Hadrosauridse 
it is apparent that the Hadrosaurince and the Saurolophince show a closer 
approach to each other than to the Stephanosaurince. These last stand 
apart with very marked and striking characteristics in about an equal 
degree from both the others. In them there is a supraorbital enlargement 
of the skull due to the surprisingly great development and backward 
extension of the premaxillaries and nasals. In the Saurolophince instead 
of a general superior enlargement of the skull there is a crest over the 
eyes, formed by the nasals in Prosaurolophus, and, according to Brown, 
by the nasals, prefrontals, and frontals in Saurolophus. 
The only one of the above listed characters common to the Saurolo- 
phince and the Stephanosaurince is the distal expansion of the ischium. 
It was this ‘‘footed’^ form of ischium, discovered by the writer in 1898, 
and first described by him in 1902^, in connexion with his original description 
of Trachodon (Stephanosaurus) inarginatus, and not until then known 
in association with any type of orthopod (predentate) dinosaur, that was 
considered by Hatcher to belong to ‘‘some member of the Theropoda’’ 
iContributions to Canadian Palaeontology, vol. Ill (quarto), pt. II. 
