Apbil 1, 1921] 



SCIENCE 



305 



publication of the Geological Survey by Dr. 

 T. W. Stanton on " The Fauna of the Cannon- 

 ball Marine Member of the Lance Formation." 

 Following the review Profesor Schuchert an- 

 nounces his opinion that the evidence 

 binds invertebrate paleontologists and geologists 

 together in the eonvietion that the Lanee and the 

 Fort Union are of Mesozoie time. The U. S. Geo- 

 logical Survey should now reverse its former con- 

 elusion and adapt itself to the fuller evidence. 



In the first conclusion Professor Schuchert 

 adopts the view of Dr. Stanton and of Messrs. 

 Lloyd and Hares, who described and named 

 the Cannonball beds in 1915, as to the Lance 

 formation, but goes even further than they 

 do in assigning the Fort Union to the Meso- 

 zoie. However, it does seem difficult to 

 justify a separation of these formations, 

 making one Cretaceous and the other Eocene. 



As a geologist long interested in the Cre- 

 taceous-Eocene problem of tlie Eocky Moun- 

 tain region, I wish to comment that Professor 

 Schuchert is not warranted in assuming to 

 speak for geologists inasmuch as he does not 

 regard much of the geological evidence. ISTor 

 does he give due weight to paleontological 

 data, aside from those of the mollusea. More- 

 over, it seems gratuitous to assume that the 

 Geological Survey, because it has not adopted 

 the conclusion reached by Professor Schuch- 

 ert, has not considered in its decisions the 

 bearing of facts concerning the Lance secured 

 by its own investigators some years ago. The 

 Survey geologists have also secured much 

 other evidence. 



Now it is perfectly well known to Professor 

 Schuchert that the question as to the age of 

 the Lance and Fort Union beds is a part of a 

 very large problem, involving a conception of 

 the geologic evolution of the whole Eocky 

 Mountain Province from Mexico to far north 

 in Canada. More than a score of more or 

 less local formations, younger than the great 

 continuous Cretaceous section and older than 

 the Wasatch Eocene, are to be correlated and 

 interpreted. These formations present a great 

 deal of varied evidence as to the history of 

 the Cretaceous-Eocene transition period. The 

 Survey has, in fact, based its action, with 



which Professor Schuchert disagrees, on a 

 consideration of all available evidence. 



Investigations of the Eocky Mountain 

 Province and adjacent lower country to east 

 and west, made within 30 years past, have 

 surely proved that the older idea of the 

 diastrophism which characterized the transi- 

 tion from the Cretaceous to the Eocene period 

 was very faulty. The change was gradual, 

 not abrupt, and, while over a large area the 

 great Cretaceous succession was ended, the 

 uplift was epeirogenic for a long period dur- 

 ing which erosion and prevailingly continental 

 deposition proceeded, and there was no such 

 abrupt environmental change affecting life 

 upon the land as has been assumed. In gen- 

 eral the newer picture of Eocky Mountain 

 development, after Laramie time, gives no 

 basis for the belief that dinosaurs and some 

 other dominantly Mesozoie land forms could 

 not survive into the Eocene. In fact, dino- 

 saurs of the type found in the Lance lived in 

 the Denver epoch, that is, they survived dur- 

 ing the period in which the entire Cretaceous 

 section was removed from a large part of 

 Colorado and adjacent regions. 



The Lance and Fort Union formations of 

 eastern Montana and adjacent portions of the 

 Dakotas present an exceptionally interesting 

 and important association of stratigraphic 

 and paleontologic data, the subject of con- 

 flicting ideas which must eventually be har- 

 monized. Their correct interpretation will 

 contribute much to our understanding of 

 Eocky Mountain history. The most striking 

 data will be briefly specified. 



The Lance in some places rests with 

 erosional unconformity on the Fox Hills 

 Cretaceous, the gap being of undemonstrated 

 extent. It may be large, and not small, as 

 Schuchert assumes. In some districts Lance 

 and Fort Union form an apparently con- 

 tinuous section reaching 5,000 or more feet 

 in thickness. In one limited area only, the 

 Ludlow lignitic and Cannonball marine shale 

 members are seen to separate the formations. 



A well defined flora runs through both 

 Lance and Fort Union. It is considered 



