110 FLORA OF THE LARAMIE GROUP. 



tlic flora of the Laramie is positively identical in its geological horizon 

 witii that of Sezanne. There are marked differences in the general char- 

 acters of the vegetable groups. The flora of the Laramie, for example, 

 has a remarkable predominance of species of palms, while these are, on 

 the contrary, very rare at Sezanne. As the palms have their origin, as 

 far as known, in the middle Cretaceous, where they have been observed in 

 very rare remains, limited to one or two species, and as their development 

 has been gradually progressing through the more recent formations, this 

 fact, or the abundance of remains of palms in the flora of the Laramie, gives 

 to it a somewhat more recent aspect than that of Sezanne, where the absence 

 of palms, however, may have resulted from mere local circumstances. 



2d. Some time ago the members of one of the scientific expeditions of 

 Princeton College discovered and collected in Wyoming a number of fine 

 specimens of fossil plants referable, by their characters, to a stage of the 

 Cretaceous more recent than the Cenomanian Dakota Group. As far as 

 can be judged by a preliminary examination, the species, mostly Quercites 

 and Araliaceoe, are related by identical types, even by some identical species, 

 to the flora of the Senonian, as it is known in Germany by the plants 

 published by Hosius and Von der Mark, and in Belgium by those of Debey. 

 They have also a degree of affinity, though less distinct, with those of the 

 Marnes Heersiennes of Gelinden, a formation which, in France, constitutes 

 part of the series of the Sables de Bracheux or of the London clay, etc.. 

 the lowest part of the Tertiary system, or Eocene, as it is generally admitted 

 to be by European geologists. The plants of Gelinden, partly Senonian in 

 their characters, are related to the Sezanne flora by one identical species 

 and a number of others of generic or typical affinity. Hence we see now, 

 in the floras of the North American Continent, from the Cenomanian to the 

 Eocene of the Laramie, a succession of vegetable groups corresponding to 

 the European series, with the exception only of the flora of Gelinden in 

 the Sables of Bracheux, not yet discovered on this continent. According 

 to French geologists the Sezanne beds are comprised in the Pisolitic lime- 

 stone, a formation superior to the Sables of Bracheux, and hence more 

 distinctly referable to the Tertiary. 



3d. A memoir published by Professor Cope on the horizon of extinct 



