LBSQUEREux.] PALEONTOLOGY— LIGNITIC FLORA AGE. 367 



plan of my former reports in tlie following manner : The specimens ex- 

 amined from the exploration of past year (1873) will be described in 

 separate sections or groups, to which are referable the localities where- 

 from they are derived ; and instead of placing in a single synoptical 

 table all the species known from our American Tertiary measures, 

 it will be more appropriate to prepare a table for each of the Tertiary 

 stages, as recognized above ; reserving a general table for a later time, 

 when our Tertiary divisions are more positively recognized. It is to 

 this last end especially, and as stated above, that these different tables 

 may be useful. The materials which we have now on hand are abun- 

 dant enough to point out a marked difference in the vegetation of the 

 different horizon of the Tertiary, though the general characters of the 

 separate groups which they represent are not yet well determined 

 enough to give positive evidence in regard to the exactness of these 

 divisions. As onr Tertiary measures are of wide extent, and are likely 

 to become more and more carefully studied, these different tables will 

 afford points of comparison for local floras, and therefore for identifi- 

 cation of local formations, just as, in the former reports, the general 

 tables furnished for the comparison of the geological epochs, the Creta- 

 ceous and Tertiary, an evidence which is needed no more ; for, indeed, 

 I believe that from the descriptions, details, and expositions of the 

 characters of each of these separate groups of the Tertiary, its age and 

 its disconnection from the Cretaceous will be established positively 

 enough to prevent any further discussion on the matter. 



§ 1.— AGE OF THE Is^OETH AMEEICAN LIGNITIC. 



Besides the evidence furnished on the age of this formation by the 

 characters of the vegetable remains, I have, in my former annual report 

 to Dr. Hayden, drawn some collateral conclusions, which I wish to briefly 

 review now, in order to separately consider, in regard to them, any new 

 evidence afforded by the researches of 1873. 



These conclusions were taken, 1st, from the fact of the immediate 

 superposition of the strata bearing plants to well-characterized strata of 

 the upper series of the Cretaceous, the Fort Pierre and the Fox Hill beds 

 of Hayden's section, in the Eeport for 1871, (p. 87.) This immediate su- 

 perposition of the heavy fucoidal sandstones and of the Lignitic over 

 Upper Cretaceous rocks, is seen in full evidence, as remarked in the re- 

 port, in the Eaton Mountains of New Mexico, around Trinidad ; all along 

 the ridge of sandstone from Trinidad to the Spanish Peak ; at the Caiion 

 City coal-basin under the Lignitic formation, as marked in the section of 

 Mr. Nelson Clark, superintendent of the coal-mines ; at Colorado Springs, 

 in following the bed of Monument Creek, from the depot to Gehrung's 

 coal ; at Golden, Marshall, &c. On this subject my observations agree 

 with those formerly recorded by Dr. Hayden, Dr. Leconte, and others; 

 the succession of the strata has been recognized by all the geologists. 



2d. I have not denied, and do not deny now, the presence of animal 

 Cretaceous remains in the strata of the Lignitic, though persisting to con- 

 sider the formation as Tertiary notwithstanding; for I regarded and still 

 regard the presence of some scattered fragments of Cretaceous shells as 

 of little moment in comparison with the well-marked characters of the 

 flora, characters which have been fully established by a large number of 

 specimgens obtained from all the localities referred to the Lignitic. I re- 

 marked, however, on the scarcity, if not the total absence, of Cretaceous 

 animal remains in the whole extent, of the Colorado basin, from the Ea- 

 ton Mountains to Cheyenne. "" 



Since then, new evidence has been supplied to this subject, first by a 



