AGE OF THE LIGNITIC DETERMINED BY ITS FLORA. 341 



recent or Miocene ones. Hence, we may consider them liere as Cretaceous 

 forms continuing into the Tertiary, like the two specmti o{ Sequoia of Califor- 

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

 that epoch that their distinction is scarcely possible, have passed, rare and 

 venerable remains of the geological times, to tlie present flora. Sequoia 

 Langsdorffii and S. brevifolia, though found in the first group, are two truly 

 Miocene Conifers. 



The Palms and the few Monocotyledones which ai-c of interest in 

 regard to the evidence of age of the Lower Lignitic are considered here- 

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



In the Dicotyledones, some generic divisions indicate a geological rela- 

 tion of their species by the exclusive presence of Eocene or Miocene types 

 in the diflerent groups. Thus, in Myrica, M. Torreyi, an Eocene type, for 

 it is related to species of Mount Bolca, is with Myrica Lessigii, a plant of 

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

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

 Miocene affinities, none are found below the fourth group. 



In the genus Po2)uh(s, P.melanariu, P. iiielanarioidcs, P. Ungeri, and P. 

 monodon, all found in localities referred to the first group, arc 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 Platanus, for P. Reynoldsii and P.rhomboidea 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 Platanus type, represented by P. Guillelmce. 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, palmately nerved leaves, has its 

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

 representatives, like F. planicostnta, are recognized in the Eocene of Suzanne 

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

 others, are either identical or closely allied to species of the lowest Miocene 

 of Europe, Bilin and Monte Promina. The genus Viburnum is represented 



