April 1, 1921] 



SCIENCE 



307 



invertebrate paleontologist to give some at- 

 tention to the possibility tbat a northern 

 isolated sea existed into early Eocene time 

 and that its conditions produced a modifica- 

 tion of the Cretaceous molluscan fauna nat- 

 urally different from that arising during the 

 same time in the Gulf region. Does not the 

 Cannonball fauna show what modification had 

 been reached at a time which, under the exist- 

 ing conditions, must be placed in the general 

 time scale by utilizing, instead of ignoring, 

 the other facts of the Lance and Fort Union 

 formations, and also the concordant knowl- 

 edge of Eocky Mountain history? 



Whitman Cross 

 Washington, D. C, 



To THE Editor of Science: In Science for 

 January 14, 1921, Professor Schuchert, in re- 

 viewing Dr. Stanton's recent paper on " The 

 fauna of the Cannonball marine member of 

 the Lance formation," proceeds to answer this 

 query in a most emphatic and unreserved 

 aiflfirmative. He assumes to speak with au- 

 thority for geologists and vertebrate and iu- 

 vertebrate paleontologists, but he admits that 

 the " floral brethren " will, of course, continue 

 to dissent. The problem of establishing the 

 line between Cretaceous and Tertiary time in 

 the Eocky Mountain province has been more 

 or less of a storm center for a number of 

 years, but the question can only be settled 

 when all the available lines of evidence have 

 been evaluated and harmonized. Drawing 

 this line at the top of the Fort Union will 

 profoundly affect other areas and other prob- 

 lems, many of which Professor Schuchert 

 appears to have underestimated if not indeed 

 overlooked. 



The faith that is in the " floral brethren " 

 is strong! This evidence has been set forth 

 at length on several occasions, but a brief 

 recapitulation may not be without interest. 

 Up to the present time, with one or two minor 

 exceptions, the Fort Union has been every- 

 where accepted as of Eocene age. It has a 

 very large flora of approximately 500 species. 

 Aside from local stratigraphic and paleonto- 

 logic considerations, the Eocene age of tlie 



Fort Union flora is attested by its affiliation 

 with many European Eocene deposits of 

 definite, acknowledged position, as Ardtun in 

 Mull, Gelinden in Belgium, and Sezanne in 

 the Paris Basin, as well as the Eocene 

 in Greenland and Alaska. This affiliation 

 amounts to many identical and closely related 

 species, as well as identical and related genera. 

 Several Fort Union species are believed to be 

 still living, a condition not known for any 

 earlier American deposit. 



The flora of the Lance formation is also a 

 rich one, comprising about 125 forms, some 

 of which, however, are so fragmentary and 

 obscure as to be incapable of more than 

 generic determination. After eliminating the 

 new forms and those that can not be specific- 

 ally named there are 87 species that are posi- 

 tively identified, all but 15 of which (about 

 80 per cent.) are found in the Fort Union. 

 It is unmistakably a Fort Union flora, and 

 occurs through the whole vertical range of the 

 Lance formation, some of the most character- 

 istic Fort Union plants being found within 

 four feet of the base of the beds. Of the 

 entire known Lance-Fort Union flora less than 

 15 species have been reiaorted from Cretaceous 

 beds anywhere, and this number will be re- 

 duced instead of enlarged by revision of the 

 floras involved. 



Sedimentation was undoubtedly continuous 

 through the Lance and Fort Union forma- 

 tions; in fact, it is impossible to draw any 

 satisfactory line between them. The highest 

 point at which dinosaurs occur is taken as 

 the top of the Lance, but where these remains 

 are absent it has no recognized or recognizable 

 top. If the Cannonball marine member of the 

 Lance formation is Cretaceous then both 

 Lance and Fort Union are Cretaceous, for 

 there is no stopping point short of the top of 

 the Fort Union. Professor Schuchert even 

 holds that there " is here a continuous and 

 unbroken series of deposits from the Pierre 

 and Fox Hills into the top of the Fort Union, 

 and that the reported erosion contacts between 

 the several formations are due to nothing 

 more than changes from marine to brackish 

 and fresh-water deposition, or to irregularities 



