68 MEMOIRS OF THE CARNEGIE MUSEUM 
guidance in the conferring of new names on new formations the theory that each 
such name should be derrved from the name of some locality at which the formation 
is well displayed and may be easily recognized and studied. It might also be well 
to remember in this connection that we are no more competent to legislate for 
future generations than were our forefathers. 
Age of the Atlantosawrus Beds. 
There has been considerable difference of opinion regarding the age of the Atlan- 
tosaurus Beds. By some they have been regarded as of Lower Cretaceous age and by 
others as Upper Jurassic. When first discovered, these beds were referred by Pro- 
fessor Marsh to the Cretaceous (see American Journal of Science, July, 1877, pp. 87- 
88). In December of this same year Professor Marsh referred these same deposits 
to the Upper Jurassic and in a note describing a new fish, Ceratodus giintheri, from 
these deposits, published in the January number of the American Journal of Sci- 
ence for 1878 he named them the Atlantosaurus beds. He ever after consistently 
maintained their Upper Jurassicage. Cope and Hayden on the other hand referred 
these beds, more especially as developed at Canyon City, Colorado, and at Morrison 
to the Dakota, now generally recognized as pertaining to the lowermost member of 
the Upper Cretaceous. The following paragraph from page 254 of the Proceedings 
of the American Philosophical Society was written by Professor Cope and it ts sig- 
nificant in this connection. It is as follows: ‘‘Dr. Hayden visited the locality of 
Mr. Lucas’ excavations (near Canyon City) and informs me that the formation from 
which the Camarasawrus was obtained is the Dakota. Professor Marsh has at- 
tempted to identify what is, according to Professor Mudge, the same horizon, one 
hundred miles north of Canyon City with the Wealden of England. Specimens 
from the northern locality which I have examined render it certain that the horizon 
is that of Mr. Lucas’ excavations. Of this I may say that there is no paleontolog- 
ical evidence of its identity with the Wealden. The resemblance of the vertebrate 
fossils to those of the English Odlite is much greater, but not sufficient as yet for 
identification.” Ten years later however (American Naturalist, May, 1887, pp. 446— 
447) Cope placed these beds in the Jurassic to which they had been previously 
referred by both Marsh and King and which, from the paragraph quoted above, 
would seem to have been the only course open to him. Indeed there is little doubt 
that when Cope first referred these beds to the Dakota he did so entirely upon the 
determinations of Dr. Hayden and regardless of the paleontological evidences 
afforded by the fauna they contained, which, such as it was, as is shown by the quo- 
tation above, he regarded as pointing to a decidedly greater antiquity even than the 
