FOSSIL FLOEAS. 701 



Calamites, Asterophyllites, and Conifers are found. Psilophytum extends 

 in America through Upper Silurian and Devonian formations. It is a 

 plant probably Cryptogamous, but not referable to any existing form, but 

 presenting resemblances to Khizocarpeae and Lycopodiaceae. Cyclostigma 

 is more distinctly Lycopodiaceous, as also Lycopodites. Conifers are 

 represented by Prototaxites, described as presenting indications of Coni- 

 ferous structure in a simpler condition than now existing. In the Upper 

 Silurian traces of Lycopods occur. 



Upper Palaeozoic, or Carboniferous System. The known floras of tins 

 system, remarkable for the presence of the great Coal-beds of Europe, 

 afford a very large number of species, in which there is a continued great 

 predominance of the Leafy Cryptogamia (Ferns, Lycopods, Equiseta, &c.), 

 in many respects of higher organization than those now existing. 



The principal characteristics revealed here are the absence of Dicotyle- 

 dons, the paucity of Monocotyledons, the predominance of the Ferns and 

 allied Classes, and of certain plants of organization not met with in ex- 

 isting vegetation, referred by some authors to the Class of GymuosDerms, 

 by others, and probably more correctly, to the vicinity of Lycopodiaceae, 

 &c. Conifers and Cycads begin to appear, with Stigmarias, Sigillarias, 

 Lepidodendron, c. The general character of this flora is very monoto- 

 nous, and alike in character from the poles to the equator. 



About 150 species of Ferns have been found in the British Coal- 

 formation. Lepidodendron has the habit and spores of Lycopodium. 

 Lepidostrobus is the fruit-spike of Lepidodendron, having the structure 

 of existing Lycopodium. Calamites seem to have been gigantic Equiseta. 

 Asterophyllitvs, Annularia, Sphenophyllum are possibly forms of Calamites. 

 Stigmaria is the root of Siyillaria, a plant of doubtful affinity, referred by 

 Carruthers to Lycopodiacese, by others to Gymnoeperms. The Conifers 

 are represented by Dadoxylon, allied to Araucaria, Sterribergia, Trigono- 

 carpum, &c. Sternbergia is supposed to have been the pith of Dadoxylon. 

 Antholites has much the general appearance of an Orobanche. 



Permian System. The fossils of the Magnesian Limestone afford only 

 fragmentary representatives of the Carboniferous flora, most of the cha- 

 racteristic genera having disappeared. The Orders are much the same, 

 but less numerously represented by species. Silicified Coniferous wood, 

 Walchia, Ferns, Calamites, Lepido'dendron, and Algae are found, and also 

 evidence of the existence of Palms. Nwggerathia has the venation of 

 Salisburia. 



2. Flora of the Mesozoic, or Secondary Strata. 



Triassic, or New Red System. In the " Variegated Sandstone " strata 

 of this formation, comparatively few species have yet been observed. 

 The Carboniferous species have disappeared; Ferns still predominate and 

 exhibit peculiar forms; Conifers (Voltzia, Haidingerd) are abundant; 

 Cycadeae rare, and a few doubtful Monocotyledons (Yuctites, Palceoxyris) 

 occur. In the "Keuper" Sandstones, with a general analogy in the 

 proportion of Orders, except that Coniferae are rare and Cycadacese abun- 

 dant, the genera of Ferns and allied Orders are mostly distinct from those 

 of the Vosgesian, or " Variegated '' Sandstones. 



Liassic System. The essential characters of this epoch are the great 



