106 EELATIONSHIP OF THE 



which the plants of the Dakota Group liave been referred, 40 are repre- 

 sented at Atane; and in them (besides Ferns, Conifers, Monocotyledons) 

 there are, in the Dicotyledons. Mafjnoliacew, Anonacew, Meiiispermaccce, 

 Vitacece, Sapindacece, Araliacece, under the subdivision of the Polypetalous; 

 Legutninosce, Ericacece, Ehenacece, in the Monopetalous: Ilamamelncece, 

 Cornacece, Rhamnacem, Urticacece f Morece Juglandece, etc. J, in the Apetalous. 

 Hence the relation of these tloras is, so to speak, general. There is only a 

 marked difference in the number of species represented in a few groups. 

 Atane, for example, has 35 species of ferns and 28 of Conifers, while only 

 6 ferns and 9 Conifers are known from the Dakota Group. This last flora 

 has a large number of species in the genera Salix. Flafarms, Sassafras, 

 Aralia. Liriodendron, Menispermitcs, Frotophyllum, while Atane has pre- 

 dominance of species in Magnolia, in the Myriacece, Pterospermites, BJtus. 

 and especially in the Leguminoso', of which 18 species are described by 

 Heer, while only one is known from the Dakota Group. But these differ- 

 ences merely show the influence of local circumstances, lower temperature, 

 more open ground perhaps for the plants of Atane, where ferns and 

 Leginninosce are more abundantly distributed than in forests of large-leafed 

 trees, like those of which the flora of the Dakota Group is especially 

 composed. 



As Kome and Atane have in common 8 species of Ferns and Gynnios- 

 perms, of wliicli two only have been found in the Dakota Group, it might 

 be supposed that the Atane flora is older than that of the Dakota Group. 

 The characters of the Dicotyledonous plants lead to a different conclu- 

 sion; for some of these plants of Atane are identical or very closely related 

 to species of the upper Cretaceous, or Senonian. while none of them have 

 been observed in the Dakota Group; Quereus Westfalica and Q. hieracifvUa, 

 recorded by Heer in the flora of Atane, are described from the Senonian of 

 Europe; two species of Dcwalquea, also recognized by Heer in the plants 

 of Atane, are found in the upper Cretaceous of Belgium and the Paleocene 

 of France, while Cinnamomum Sezannense, which Heer has also found in 

 the plants of Atane, is lower Eocene in France. Therefore, it is evident 

 that the formation of Atane is somewhat more recent than that of the 

 Dakota Group, apparently an upper stage of the same. 



The degree of relationship of the Dakota Group flora with that of the 



