WARD] HISTORICAL REVIEW OF OPINION. 415 



tively ascertainiug the age of the lignitic formations." He visited most 

 of the importaut points in Wyoming, Colorado, and New Mexico, and 

 prepare<l an elaborate report, in which, it is needless to say, he confirmed 

 and reasserted his former couclnsious as to the Tertiary age of the en- 

 tire coal bearing series, which he denominates the American Eocene.' 



The reports of Messrs. Meek and Bannister were also published in 

 the same volume. The former expresses himself with his usual cauMou, 

 admitting that the invertebrate fossils were inadequate to determine 

 the age of this group, and that his former reference of certain species 

 to the Cretaceous was not prompted by the evidence afforded by the 

 forms tliemselvec (pp. 457, 458). Some of the statements made in this 

 report have acquired special interest in the light of recent investiga- 

 tions and in view of the gradual settlement of opinion which seems to 

 be now going on respecting this much discussed question. He says 

 (p. 460) : "The most surprising fact to me, supposing this to be a Cre- 

 taceous formation, is, that we found directly associated with the reptil- 

 ian remains at Black Buttes a shell I cannot distinguish from Viriparus 

 trochiformis, originally described from the Lignitic formation at Fort 

 Clarke, on the Upper Missouri, a formation that has always been re- 

 garded as Teitiary by all who have studied its fossils, both animal and 

 vegetable. * # * The occurrence of this last mentioned species here, 

 along with a Cretaceous type of reptilian, and a Corbicula apparently 

 identical with G. ('^//(eri/brwn's of the Judith Eiver brackish-water beds, 

 together with the presence of Corbiculas very closely allied to Judith 

 River .species, at lower horizons in this series, and the occurrence of 

 some vertebrates of Cretaceous affinities at the Judith River localities, 

 would certainly strongly favor the conclusion, not only that this Judith 

 formation, the age of which has so long been in doubt, is also Creta- 

 ceous, but that even the higher freshwater lignite formation at Fort 

 Clarke and other Upper Missouri localities may also be Upper Creta- 

 ceous instead of Lower Tertiary." 



From these and other expressions in this report Mr. Meek may be 

 fairly said to have conceded the Cretaceous age of the Bitter Creek 

 series, but he insists that the Judith River deposits must go with it 

 into that formation, while of the Fort Union group his position may be 

 summed up by quoting his remark that it would take very strong evi- 

 dence to convince him ''that the higlier fresh-water Lignite series of 

 the Upper Missouri is more ancient than the Lower Eocene." 



The year 1874 found the discussion of the age of the so-called Ameri- 

 can Lignitic at its height. A paper in the American Journal of Science 

 for April of that year, by Dr. Newberry, and a reply to it by Mr. Lesque- 

 reux in the same journal for June, deserve special attention. The for- 

 mer makes bold to say that to his "certain knowledge" a considerable 

 portion [that of New Mexico] of the flora which the latter had called 



'Annual Report of the United States Geological Survey of tlie Territories, 1872, pp. 

 3;il), 343. 



