WAK...] DISCUSSION OF THE TABLE. 629 



aud Lower Yellowstone. As the.se latter were, and by many are still, 

 regarded as Miocene, and certainly contain a flora differing in many re- 

 spects from the rest, the general coujplexion of the whole will be con- 

 siderably modified by including them. 



By inspecting the table we observe that only a single species, Sequoia 

 Lany.sdorfii, is common to all three of the formations. This species is 

 generally northern in the western hemisphere, but it is found in the 

 Laramie at Black Buttes, hi the Fort Union group, and in the northern 

 extension of this latter in British America. It also occurs in the Cre- 

 taceous deposits of Nanaimo, Vancouver Island, and in the Seuonian 

 beds of Patoot, Greenland. Professor Gardner finds it in the Eocene 

 deposits of the Isle of Mull, and Massalongo enumerates it in his Mio- 

 cene flora of Senegal. 



Only one other Laramie species, Giiikyo polymorpha, is found in any of 

 the Senouian beds, and this occurs also at Nanaimo. Its Laramie lo- 

 cality is the place near Fort Ellis in Montana designated as " six miles 

 above Spring Canon," which we have seen reason to regard as a west- 

 ern member of the great Fort Union deposit. 



The number of Laramie species that also occur in the Eocene as de- 

 fined in the table is quite large, amounting in all to thirteen or fourteen. 

 Seven of these are confined to these two formations, which might afford 

 strong prima facie evidence of the close affinities of the Laramie and 

 Eocene floras. This evidence, however, is greatly weakened when we 

 perceive that of these seveu four occur in the supposed Eocene beds 

 of Mississippi aud not in any of the Old World deposits. This is cer- 

 tainly strong proof of the close relationship of these Mississippi beds 

 to those of the Laramie, as well as of their similarity of age, but it 

 is more interesting as showing that in those early times one great ho- 

 mogeneous flora stretched all the way across the North American con- 

 tinent, and that similar forests fringed the waters of the Gulf of Mex- 

 ico during their southward retreat, and those of the Laramie Sea as it 

 shrunk to the proportions of inland lakes. The difference of time be- 

 tween the two deposits, though it might have been great, was not suf- 

 ficient to alter the specific identity of these four forms aud doubtless 

 of very many others, while in other cases the Laramie species may 

 represent the ancestors of the Eocene species found or to be found in 

 the more eastern deposits. These species are, Sahal Grayanus, Populus 

 monodon, Magnolia Hilgardiana, and M. Lesleyana, all of Lesquereux. 

 All except MaguoUa Hilgardiana occur onlj' in the typical Laramie 

 deposits of the more southern districts, but this species has now been 

 rej)orted also from the Yellowstone Valley, which, of course, relegates 

 it to the Fort Union group. 



The other three Laramie species which are otherwise confined to the 



Eocene are Eulymenites minor, found in the Flysch of Switzerland, Fieus 



Dabnatica, found in the supposed upper Eocene beds of Monte Promina 



in Dalmatia, which some authors place higher, and Sterctilia modesta of 



6 GEOL 34 



