HATCHER: OSTEOLOGY OF HAPLOCANTHOSAURUS 67 
accomplish considerable changes in the dinosaurian fauna of this region, and these 
changes are readily apparent in the faunas from these two horizons, though for 
obvious reasons the present paper is not the place in which to discuss them. They 
will no doubt be fully recognized and discussed by Professor H. F. Osborn in his 
Monograph on the Sauropoda now in course of preparation for the United States 
Geological Survey. 
Synonymy of the Atlantosawrus Beds. 
Although these beds were first recognized, named and adequately described both 
lithologically and faunally, by Professor Marsh they have received several different 
appellations by subsequent authors. Scott has called them the Como-beds ; by Cross 
they were referred to as the Morrison beds; Jenney named them the Beulah Shales 
and this name was used by Darton. Considering the usual similarity of the faunal 
and lithologic features of these beds wherever they are known to exist and the ease 
with which they may be recognized even at different and widely separated locali- 
ties, it would seem somewhat unfortunate that they have received so many names. 
Since Marsh’s term the Atlantosawrus beds has priority, and has become well 
known through long and general usage there would seem no good reason why it 
should not be retained. Even should the reptilian genus Atl/antosawrus, as contended 
by some but which has yet to be demonstrated, prove to be a synonym and have to 
be abandoned, this would not invalidate the name of the formation. It would be 
quite as reasonable to maintain that since Fort Union on the Missouri River from 
which the Fort Union beds took their name, is no longer in existence that this great 
formation should receive a new name. While the present writer is entirely in favor 
of basing all new formation names on geographic names taken from the localities 
where such formations are first studied or are best represented, it does not appear 
desirable to make this rule retrogressive. Such retrogressive application of this 
rule would not only work an injustice to many pioneers in American geology, but 
what is of even greater importance, it would result in augmenting still further that 
confusion which already exists in our geologic formation names. Surely from that 
standpoint alone there is sufficient reason for deprecating any attempt to duplicate 
such names. Nor does the plea advanced by some who have been most active in 
giving new names to old and well known formations, that it is easier to give a new 
name than to turn bibliographer and trace out the synonymy and priority of the 
names already given by others, give promise of being justified by the results which 
are sure to follow such a course. ‘To the present writer it would appear much the 
better plan to accept formation names for formations already known, as we find them 
having due respect for priority and general usage; to adopt as a general rule for our 
