67 
Montana. No characters can at present be assigned to Trachodon beyond 
those derived from the single mandibular tooth which constitutes the 
type.i 
Edmontosaurus rivalled in size its bulky contemporary Hypacrosaurus. 
It appears, however, not to have been as large as Prosaurolophus, from the 
Belly River formation of Alberta, if the skull in the Hadrosauridse can be 
considered a criterion of the size of the animal as a whole. 
CLASSIFICATION OF THE HADROSAURID.E. 
DIVISION INTO THREE SUBFAMILIES. 
The discovery in recent years of many new generic forms of Hadro- 
sauridse in the western Cretaceous of this continent, more especially in 
the Belly River and Edmonton formations of Alberta, has greatly enlarged 
the list of known genera of these herbivorous dinosaurs, and has been the 
means of increasing our knowledge of their osteology. As a result of the 
study of these forms it is apparent that three principal groups or sub- 
families are represented. 
In 1914^ a classification of the Hadrosauridse (Trachodontidse) was 
proposed by Mr. Barnum Brown who recognized two subfamilies, viz., 
the Trachodontince and the Saurolophince. Since then, principally through 
the discovery (1915) and further study of Cheneosaurus, the discovery in 
1917 of a nearly perfect skull of Stephanosaurus, and the additional study 
of the family as a whole, greatly assisted by the well-preserved specimens 
in the collections of the Geological Survey, it has become evident that 
certain forms included in the Saurolophince differ from the Saurolophus 
type in so many fundamental particulars that their withdrawal to form 
a new subfamily is necessary. For this third subfamily of the Hadro- 
sauridse the name Stephanosaurinoe is proposed, to include the genera 
Stephanosaurus Lambe, Corythosaurus Brown, Cheneosaurus Lambe, and 
probably Hypacrosaurus Brown. Under the proposed new classification 
the Saurolophince are represented by Prosaurolophus Brown, and Saurolo- 
phus Brown. The Hadrosaurince {Trachodontince Brown) embrace Grypo- 
saurus Lambe, Kritosaurus Brown, Edmontosaurus Lambe, “Claosaurus” 
Marsh, and Diclonius Cope. 
The characters denoting the resemblances and dissimilarities of the 
three subfamilies, as provided principally by the skull, are as follows: 
i“On the genus Trachodon of Leidy,” by L. M. Lambe, Ottawa Naturalist, vol. XXXI, No. 11, February, 
1918. 
2Bull. Am. Mus. Nat. Hist., New York, U.S.A., vol. XXXIII, art. XXXV. 
