Lee — Recent Discovery of Dinosaurs in the Tertiary. 533 



the Cretaceous purely on the basis of the dinosaurian remains. 

 It is possible that a few will still insist that because of the 

 presence of Ceratopsian dinosaurs, the Dawson should be re- 

 ferred to the Cretaceous in spite of its stratigraphic relations, 

 in spite of its other vertebrate remains, and in spite of the evi- 

 dence of its fossil flora, but the writer ventures to hope that 

 better counsel will prevail. Because of this possibility it may 

 not be out of place in this connection to recall that Gardner* 

 found dinosaurs of the typical " Ceratops beds" fauna in beds 

 lying tk unconformably above the 'Laramie' and below the 

 Wasatch" at Ojo Alama in northwestern New Mexico, and 

 also in rocks in similar position near Dulce, New Mexico, and 

 that Leef also found a dinosaur near Durango, Colorado, in 

 beds supposed to be of the same age4 It seems probable, 

 therefore, that in the southern part of the Rocky Mountain 

 region some of the dinosaurs occur normally above a great 

 unconformity, as they do in so many places in the northern 

 part, and that this unconformity may be general thoughout the 

 Rocky Mountain region. These recent finds tend to confirm 

 Knowlton's§ statement that the fauna represented by Tricera- 

 tops and its associates is found only above an unconformity. 



Whether a certain formation shall be regarded as Cretaceous 

 or Tertiary is largely a matter of definition, and there seems to 

 be little hope of unanimity of opinion as to where the line of 

 separation between these two systems should be drawn in the 

 Rocky Mountain region. But in the light of recently acquired 

 information the statement made by Chamberlin and Salisbury! 

 regarding the age of the Denver and Arapahoe formations 

 applies at the present time, with increased force, not only to 

 these but to the Dawson and other Triceratops-bearing beds, 

 namely : " If the presence of saurian fossils demonstrates the 

 Cretaceous age of the beds containing them, the Arapahoe and 

 Denver beds are Cretaceous ; but every other consideration 

 seems to point to their reference to early Tertiary." 



Heretofore the principal argument for including the dinosaur- 

 bearing formations in the Cretaceous has been the presence of the 

 dinosaurs, but this argument is now invalidated by the presence 



* Gardner, James H. : The Puerco and Torrejon formations of the Nacimi- 

 ento group, Jour. Geology, vol. xviii, p. 734, 1910. See also Brown, Bar- 

 num : The Cretaceous Ojo Alamo beds of New Mexico with description of 

 the new dinosaur genus Kritosaurus, Am, Mus. Nat. Hist., Bull., vol. 28, 

 pp. 267-274, 1010. 



f Lee, W. T. : Stratigraphy of the coal fields of northern central New Mex- 

 ico, Geol. Soc. America, Bull., vol. xxiii, p. 619, 1912. 



JOp. cit., p. 592. 



§Knowlton, F. H.: Where are the Laramie dinosaurs ? Science, new ser., 

 vol. xxxiv, p. 319, 1911. 



|| Chamberlin, T. C, and Salisbury, R. D. : Textbook, vol. iii, p. 158, 

 1906. 



Am. Jotjr. Sci.— Fourth Series, Vol. XXXV, No. 209.— May, 1913. 

 37 



