30 UNITED STATES GEOLOGICAL SURVEY— TERTIARY FLORA. 



Tertiary of Europe, and are even very closely allied to species of that age 

 found in the Paris Basin; while, on the other hand, one species seems to be 

 conspecific vi'ith, and two congeneric with (and closely related specifically to), 

 forms found in brackish-water beds on the Upper Missouri, containing ver- 

 tebrate remains most nearly allied to types hitherto deemed characteristic of 

 the Cretaceous. 



"That one species of Anomia found in it is very similar to a Texas Creta- 

 ceous shell, and perhaps specifically identical with it; while a Viviparus, 

 found in one of the upper beds, is almost certainly identical with the 

 V. trochifortnis of the fresh-water Lignite formation of the Upper Missouri, 

 a formation that has always, and by all authorities, been considered Tertiary. 



"That the only vertebrate remains yet found in it are those of a large 

 reptilian (occurring in direct association with the Viviparus mentioned above), 

 which, according to Prof Cope, is a decidedly Cretaceous type, being, as he 

 states, a huge Dinosaurian." 



" It thus becomes manifest that the paleontological evidence bearing on 

 (he question of the age of this formation, so far as yet known, is of a very 

 conflicting nature, though, aside from the Dinosaurian, the organic remains 

 favor the conclusion that it is Tertiary." 



Prof Cope has surveyed with the greatest care the whole series under 

 consideration, and found, from the lowest marine coal-bearing formation 

 to the Saurian bed of Black Buttes, an uninterrupted Cretaceous fauna, as 

 indicated by remains of vertebrate animals. He therefore, after considering 

 the facts exposed in favor of both opinions on the Cretaceous or the Tertiary 

 age of this Lignite of the Bitter Creek series, comes to the conclusion that 

 there is no alternative but to accept the results, that a Tertiary flora was 

 contemporaneous with a Cretaceous fauna, establishing an uninterrupted 

 succession of life across what is generally regarded as one of the greatest 

 breaks in the geological times.* 



As no kind of Cretaceous animal remains have been discovered in the 

 Lignite of Colorado, none either in that of the north, generally called the Fort 

 Union group, the question of age essentially bears upon that Bitter Creek 

 series. The line of demarkation between the Cretaceous and the Tertiary 

 is placed by Prof Cope above the Black Buttes Saurian bed. Prof King 

 fixed it in the middle of the series, near Point of Rocks; and, from my 



* Annual Report, 1873, p. Hi. 



