154 KnoivUon — The Fossil Flora of tJie Bozeman Coal Field. 



close, simple veins emerging at an acute angle from it. Asso- 

 ciated with these leaves were a small number of beautifully per- 

 served leaves, rei^resenting an undescriljed sjjecies of Thinnfeldia, 

 which is long-lanceolate in outline, tapering gradually below 

 into a tliick petiole and aljove into a long, slender acuminate 

 apex. The nervation is the same as in the preceding species. 

 In the same beds with these leaves Avere found two fruiting cat- 

 kins, at first thought to represent the fruit of the Thinnfeldia, Init 

 later decided to represent an undescribed species oi Poind as. 



Perhaps the most interesting specimens are a number of ferns 

 representing the fruiting condition of what has been called 

 Sphenopterb lakesit Lx., one of the most characteristic species of 

 the Denver formation of Colorado, but now shown to 1)0 an 

 Aspidium. At least one-tenth of all the specimens in a very 

 large collection of plants from the Denver formation belong to 

 this As'pidium Inkesii Lx. sp.''~ 



The principal object of this investigation was to ascertain the 

 light thrown by the plants upon the question of the age of the 

 deposits. Lesquereux referred the plants to his Lower Lignitic 

 or true Laramie.* On the other hand. Professor Ward would 

 incline to place them in the Fort Union beds ; l;»ut it is now 

 known that he included in his enumeration localities in and 

 about the Yellowstone Park which l)elong to a higher horizon 

 than the Bozeman Coal Field. 



Of the 43 species making up this flora, 3 are new to science _ 

 and 9 others have never been found outside of these beds, leav- 

 ing 31 species upon which we must depend in determining the 

 age. Of this number 7 species, of which 3 are doubtful, have 

 been found in the Fort Union beds, 14 in the undoubted Denver 

 formation, 12 species at Carbon and Evanston, Wyoming, the age 

 of which may be Denver, and 19 of the species in the true 

 Jjaramie. By combining the species common to the undisputed 

 Denver and the localities of Carbon and Evanston we have 19 

 species, or the same number as found in the true or coal-bearing 

 Laramie. From tins it a})iiears that there can l)e no question 

 but that it l)elongs to what is generally known as the Laramie, 

 but the evidence of the fossil plants is hardly sufficient to permit 

 a separation into the lower and iii)])cr divisions or the true 

 I^aramie and the recently differentiated Denver formation. 



*A11 of the new or interesting species will be named, fnlly described, 

 and illustrated in Bull. U. S. Geological Survey, No. — . In preparation. 

 * Hayden's Ann. Kept., 1872, p. 409. 



