300 
formation. In addition to these, Barnum Brown has described from the 
Hell Creek beds a large stegosaur, Ankylosaurus magniventris, the type 
of a new family. We can not doubt that some day a closely related form 
will be discovered in the Judith River beds; and indeed, its immediate 
ancestor may be Lambe’s Stereocephalus tutus, from the Belly River de- 
posits. 
The large herbivorous dinosaurs, the Hadrosauridze, which were ac- 
customed to walk about on their hinder limbs only, are, according to 
Cope’s identifications, represented in the Judith River formation by about 
nine species. The Lance Creek and the Hell Creek beds furnish three or 
four species of the family, most of which are referred to the genus Hadro- 
saurus, ovr T'rachodon. Whether or not there are species common to the 
two formations cannot now be definitely determined; but certainly their 
relationships are very close. 
Of all the dinosaurs that are found in the formations in which our 
interest is now centered the Ceratopsia have received the most careful 
study. What the present state of knowledge is with regard to these re- 
markable reptiles, may be learned from Hatcher’s monograph of the 
group, completed and edited by Dr. Lull (Mon. 49, U. S. Geol. Surv.). 
Unfortunately much needs yet to be learned about them, especially about 
those of the Judith River forms. Approximately nine species are known 
from the Judith River deposits of Montana and British America; and 
about fifteen species are credited to the Lance Creek beds, of Wyoming, 
and to the Arapahoe and the Denver, of Colorado. Tatcher and Lull con- 
clude that those of the Judith epoch are somewhat more primitive than 
those of the beds higher up, being somewhat smaller, with a less completely 
developed nuchal frill, with the nasal horn relatively larger and the 
supraorbital horns relatively smaller than in the younger forms. It is, 
however, to be noted that the nasal horn of Ceratops, of the Judith River 
epoch, is not yet certainly known. For the most part the genera are 
based on the characters mentioned above. They may have the importance 
assigned to them, but they do not indicate radical differences. Such differ- 
ences might easily have arisen during an interval of moderate duration. 
There can be no doubt that the Ceratopsia of the higher beds were derived 
directly from those of the lower. 
The possibility may be fully granted that further investigations may 
prove that few or no species of vertebrates continued from the Judith 
