532 Lee — Recent Discovery of Dinosaurs in the Tertia?y. 



reiterated the opinion expressed years ago, that the Denver 

 and related formations are of Tertiary age. 



Richardson states in the paper just cited (p. 272) that he 

 found a mammalian bone in the Dawson arkose which, accord- 

 ing to Gidley, is characteristically Creodont. Gidley says of 

 it : " From our present knowledge the type represented could 

 not be older than Wasatch." Although the bone was not 

 found in place, there is no reasonable doubt that it weathered 

 from rocks near by, and inasmuch as there is no remnant of a 

 younger formation within many miles of the locality where 

 it was found, it seems certain that it came from the Dawson 

 arkose. This is further emphasized by the fact that the bone 

 has perfectly fresh surfaces and shows no evidence of having 

 been transported. In the same paper (p. 275) Richardson 

 points out the fact that certain dinosaur bones collected by 

 Marsh many years ago in Monument Park, north of Colorado 

 Springs, must have come from the Dawson arkose, but these 

 bones seem to have been lost. 



During the past summer (1912) the writer had the opportu- 

 nity of visiting the locality where the Creodont bone was found 

 and there collected the remains of turtles and of dinosaurs. 

 The turtles were examined by Dr. O. P. Hay and the dinosaurs 

 by C. W. Gil more. In his report on the fossils Mr. Gilmore 

 says : " The collection consists of fragmentary Ceratopsian 

 bones, none of which is sufficiently characteristic to determine 

 the genus to which it belongs, and one ungual phalanx is doubt- 

 fully regarded as pertaining to the dinosaur Trachodon. Two 

 small shell fragments show the presence of hard and soft shell 

 turtles. Of these Dr. Hay says, ' the soft shell resembles those 

 of the Lance formation ; the other resembles those from the 

 Wasatch but is too fragmentary to be certain of its affinities.' ' 



We have then at this locality, near Colorado Springs, in beds 

 that lie unconformably on the Laramie and extend laterally 

 across the eroded edges of older formations to the pre-Cambrian 

 crystallines, a flora that correlates the beds with undoubted 

 Eocene on the one hand, as Knowlton's data given in the accom- 

 panying paper show so convincingly, and on the other with the 

 Denver and Arapahoe formations ; a mammal of a type not 

 known heretofore to be older than Wasatch; one turtle whose 

 nearest known allies are in the Wasatch fauna ; another that 

 resembles those of the Lance fauna; and dinosaurs that have 

 been somewhat generally regarded as indicative of Cretaceous 

 age but which occur in associations that convince some geologists 

 that they are Tertiary. Considering this association of fossils in 

 connection with the great unconformity, it seems wholly irra- 

 tional longer to regard a formation as Cretaceous merely because 

 it contains dinosaurs. To some geologists it seemed equally irra- 

 tional years ago to refer the Denver and Arapahoe formations to 



