STRATIGRAPHIC POSITION OF JUDITH RIVER FORMATION 751 
of his belief that two thousand feet of marine shales and sandstone of 
Bearpaw and Fox Hills age intervene between the Judith River beds 
and the Laramie [Lance] formation. These deposits, in his opinion, 
represent a period of subsidence during which the advancing sea 
drove the land animals to the west and north. He says:" 
Of these creatures which link the Judith River and Laramie [Lance] 
faunas, no remains have thus far been found so that we have no record of the 
evolution which must have occurred during the period of subsidence. At the 
close of the Fox Hills epoch, conditions much like those of the Judith River 
times again prevailed, and the horned dinosaurs, among other forms, sought 
their ancestral haunts. Four genera of Laramie [Lance] Ceratopsia are known, 
ranging themselves into two races or phyla which underwent a parallel evo- 
lution. 
In this connection my friend Mr. J. W. Gidley of the U.S. National 
Museum has kindly prepared for me the following statement: 
Regarding the validity of the Ceratopsia phyla as worked out by R. S. 
Lull, it seems to me to be highly conjectural and not founded on a basis of 
valid reasoning. While it may be conceded that Ceratops is in general more 
primitive genus than Triceratops, it is highly improbable that, having already 
developed a far greater nasal horn than in any species of the latter genus, this 
horn should have become atrophied while the brow horns were being devel- 
oped to become the principal ones. Only that Ceratops is supposed to have 
come from much older beds, it would be just as reasonable to suppose that the 
reverse might have been the case, and so far as the horns alone are concerned 
Ceratops might just as well have been the descendant of a Triceratops form. 
It seems far more reasonable to suppose that, whether contemporaneous or 
separated by a long time interval, Ceratops and Triceratops represent two 
quite distinct phyla, developing horns along different lines. 
As already intimated, the principal cause of confusion is to be 
found in erroneous ideas as to the stratigraphic position of the beds 
from which the collections were made. As a matter of fact, how- 
ever, the time has not yet arrived when the phyla can be correctly 
constructed. Not only is the material already in hand too frag- 
mentary, but it is too meager in the number of forms supposedly 
identified, nor are there sufficient specimens of each species to 
determine the distinctions due to individual variation or to differ- 
ences in sex or age. When we find that Ceratops and Triceratops 
(one of which is supposed to be ancestral to the other) were con- 
t Ibid., p. 4. 
