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SCIENCE 



[N. S. Vol. LIII. No. 1370 



clearly Eocene by EJiowlton. This view was 

 not seriously opposed until the flora, first 

 found in the Fort Union, was traced down 

 through the Lance almost to its base. The 

 flora thereby lost much of its interest to verte- 

 brate and invertebrate paleontologists, but not 

 to paleobotanists or geologists. 



The Fort Union beds have a mammalian 

 fauna of small forms considered to prove the 

 Eocene age of the strata containing them 

 until allied types were found in the Lance 

 associated with dinosaurs and other sup- 

 posed Cretaceous forms. The signiflcance of 

 the poor little mammals has seemed to dis- 

 appear, from certain standpoints, but not 

 from all. The Ceratops fauna of the Lance 

 is closely similar to that of the Denver beds, 

 correlated by the Geological Survey, together 

 with other Colorado and New Mexico forma- 

 tions, with the early Eocene beds of the Gulf 

 region. 



The Cannonball shales demonstrate the 

 temporary return of marine waters from an 

 unknown and as yet undiscussed region to 

 the Dakota district, after an absence which 

 was of considerable duration. Where was 

 this sea meanwhile? The known Cannonball 

 fauna consists of two sharks, several corals 

 and foraminifera, all of which range into the 

 Tertiary, and 60 molluscan species. The 

 molluscan group, according to Stanton, has 

 " the general aspect of a Tertiary fauna," 

 but he considers 24 species to be identical 

 with forms in the Eos HiUs or Pierre 

 formations of the Cretaceous nearby, while 

 not one is identical with any known form in 

 the lowest Eocene of the Gulf region and 35 

 are new species. 



Dr. Stanton has given, in the excellent pub- 

 lication reviewed by Professor Schuchert, a 

 careful description of the Cannonball fauna 

 and discussed its relationships to Cretaceous 

 and Gulf Eocene faunas. Elsewhere he has 

 discussed the age of the Lance on general 

 grounds but he has always given the greatest 

 weight to the character of the invertebrate 

 fauna, as is natural considering his special 

 point of view. 



Professor Schuchert has gained wide repu- 

 tation for his broad studies in paleogeogi-aphy. 

 His mature opinion was no doubt expressed 

 in his " Text-book of Geology," (1915, p. 581) 

 where he says: 



It is, therefore, the principles of diastrophism 

 and paleogeography that will eventually correctly 

 define the periods or systems. 



It may seem at first thought that this prin- 

 ciple guided Professor Schuchert in his opin- 

 ion that two paleogeographic maps presented 

 by Stanton " are a most striking summation of 

 the problem in hand . . . ." That judgment 

 seems, to the writer, far from the truth. 



One of these maps (after Schuchert) repre- 

 sents the Pierre Cretaceous ocean as extend- 

 ing from the Gulf of Mexico through the 

 Eocky Mountain region far toward the Arctic, 

 with a land barrier reaching from the east 

 at least to the boundary of Colorado and New 

 Mexico. This barrier may have extended 

 further. The other map shows the supposed 

 early Eocene limits of the Gulf sea and the 

 geographic position of the Cannonball area. 

 Wliat is needed is a paleogeographic map, or 

 several of tliem, to express a reasonable 

 hypothesis of the course of retreat of the sea 

 as the land barrier rose and apparently cut 

 ofi entirely a resti-icted northern ocean from 

 the Gulf sea, perhaps before Fox Hills time. 

 Somewhere there was an open sea, insisted on 

 by Dr. Stanton, cut off from the Atlantic- 

 Gulf ocean, in which the Fox Hills fauna was 

 modified to that found in the Cannonball. 



Unfortunately Dr. Stanton does not discuss 

 the origin, the position, the extent, or the 

 climatic and other conditions of the open sea 

 in which this modification took place. He 

 considers that the Fox Hills is the approxi- 

 mate equivalent of the upper part of the 

 Exogyra costata zone, which is near the upper 

 limit of the Cretaceous in the Atlantic-Gulf 

 region. He nevertheless recognizes " consider- 

 able differences " in the faunas, which he 

 attributes to lithologic facies, geographic 

 separation, and possibly to climate. 



It seems to a geologist necessary for the 



