298 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Yol.vi. 



single species ; of Ehizocarpae, many specimens of Salvinia Alleni, de- 

 scribed from Florissant and Elko, Nev. ; of Musci, Hypnum Haydeni, 

 likewise known only from this locality; and of Gharaceae, two specimens 

 of a Chara. 



M. Lesquereux has also found large numbers of leaves of a peculiar 

 plant without any kind of neuration, which is apparently referable to 

 the Proteeae. 



We have thus from 90 to 100 species of plants already recognized from 

 these Florissant beds, of which nearly half the species belong to the 

 apetalous exogens. About 40 of the species are figured in the Tertiary 

 Flora of Lesquereux. 



According to this writer, such an assemblage of plants indicates a 

 climate like that of the northern shores of the Gulf of Mexico at our 

 epoch. " The preponderance of conifers, of shrubs, * * * of trees 

 of small size, * * * gives to the flora a general aspect which recalls 

 that of the vegetation of u])lands or valleys of mountains." Palms are 

 almost entirely absent, only a single specimen of one species of Sabal 

 having occurred. " The leaves of some species are extremely numerous, 

 none of them crumpled, folded, or rolled, as if driven by currents, but 

 flat, as if they had been imbedded in the muddy surface of the bottom 

 when falling from the trees or shrubs along the borders of a lake." 



It is remarkable for the almost complete absence of hard fruits ; and 

 this, with the presence of flowers, of unripe carpels of elm and maple, 

 and of well-preserved branches of Taxodium, which in the living species 

 " are mostly detached and thrown upon the ground in winter time or 

 early spring," led Mr. Lesquereux to believe that the deposition of the 

 vegetable materials took place in the spring time, and that the lake 

 gradually dried during summer. 



To this we may add that the occurrence of Acorns, of Typha, and es- 

 pecially of Potainogetou, leads to the conclusion that the water of the 

 lake was fresh, and not saline or brackish, equally proved by the fish, 

 according to Gope, and by the presence of larvae of Odonata and other 

 insects whose earlier stages are passed only in fresh water. 



Neither the groups of fishes which have been found, nor the water- 

 plants, tha water-insects, nor the Planorbis exclude Mr. Lesquereux's 

 suggestion of the aunual drying of the body of the lake. Moreover, cer- 

 tain thin layers are found overlying coarser deposits, which are sun- 

 cracked through and through ; but on the other hand the thickness of 

 the paper shales, upon which most of the fossil remains are found, and 

 which are comi)Osed of uniform layers of triturated flakes of volcanic 

 products, being necessarily the result of the long- continued action of 

 water, excludes this idea. The structure of the rocks rather indicates 

 a quiet dejposition of the materials in an unruffled lake through long- 

 periods, interrupted at intervals by the influx of new lava-flows or the 

 burying of the bottom sediments beneath heavy showers of volcanic 

 ashes. 



