AGE OF THE LIGNITIC DETERMINED BY ITS FLORA. 341 



recent or ]\Ii()C(Mie ones. Iloncc, we may consider tliem here as Cretaceous 

 Cornis continuin<r into the Tertiary, like the two s\iccwii of Sequoia of Califor- 

 nia, which, representatives of the Tertiary, or so closely allied to species of 

 that <'po(h that their distinction is scarcely |)ossible, have passed, rare and 

 veneral)Ie remains of the geological times, to the present flora. Sequoia 

 LangMloiffii and S. brevifolia, tiiough found in the first group, arc two trnly 

 Miocene Conifers. 



The Palms and the few Monocolijkdones which arc of interest in 

 rcmrd to the evidence of age of the Lower Lignitic arc considered here- 

 aiter in the remarks on the flora of Point of Rocks. 



In the Dii-ot)//edo)u:s, some generic divisions indicate a geological rela- 

 tion of their species l)y the exclusive presence of Eocene or Miocene types 

 in the ditferent groups. Thus, in Mijrlca, M. Torreyi, an Eocene type, for 

 it i.s related to species of Mount Bolca, is with Mi/rica Lessigii, a plant of 

 a remarkable character, and as yet of uncertain relation, the only species 

 .)f the genus found in the Lower Lignitic; while, of ten other species of 

 Miocene affinities, none are found below the fourth group. 



Li the genus Pointhi.s, P. melanaria, P. ?nelanarioides, P. Ungeri, and P. 

 monodon.ixW foinid in localities referred to the fir.st group, are Eocene or low- 

 est Miocene types of Europe. P. mutabilis is of wide distribution; and, of 

 six other species of this flora, all Miocene, none are represented in the Lower 

 • Lignitic. We have the same difference in regard to the distribution of the 

 species of Plntanus, for P. Rcynoldsii and P.rhomhoidca are of a peculiar type, 

 without any relation witli that of the species found in the upper groups; 

 even P. Haydenii, with its leaves sometimes without lobes, or merely dentate, 

 may be considered as proper, like the two others, to the American Eocene. 

 The Miocene Platnnus type, represented by P. GmUelmcR and P. aceroides, 

 is not found lower than the third group. In Ficus, two distinct types are also 

 remarked in the species described in this Flora. The first, that of the lan- 

 ceolate leaves, appears in the Miocene or upper groups; the other, with broad 

 ovate-lanceolate, generally more or less cordate, palmatcly nerved leaves, has its 

 species nearly exclusively in the Lower Lignitic. Some of its most abundant 

 rei)rcscntatives, like F. planicoitnta, are recognized in the Eocene of Sdzanne 

 as in that of the Mississippi; others, like F. Dahnatica, F. asarifolia, and 

 others*, arc either identical or elcsely allied to species of the lowest Miocene 

 of Euroite, IVilin and Monte Promina. Tlie genus Viburnum is represented 



