middle silurian, at Angers, in France. The first evi- 

 dence of a Lycopodiacea occurs in the upper Silurians of 

 Canada, Psilophyton, Daw, a dichotomous branched 

 plant with slender bifurcating stems proceeding from a 

 horizontal rhizome ; the surface of the stem is destitute 

 of scars, but marked with spiral ridges, as if rudimentary 

 leaves. The internal structure of the axis shows 

 loose cellular tissue sunounded by a cylinder of 

 elongated woody cells without distinguishable 

 pores, but with traces of spiral fibres, which 

 point not only to its affinity with the Lycopodiacese 

 but especially with the recent Psilotum, a genus 

 of club-mosses found in America and Australia. 

 The rhizomata of this ancient plant occur in situ in a 

 number of argillaceous beds, in a manner which shews 

 that they crept in immense numbers over flats of sandy 

 clay, which were frequently inundated. The succeeding 

 devonian age produced several new forms of plants 

 which, with few exceptions, generally resemble those 

 of the coal-measures, among which a single species of 

 the genus Lepidodendron may be mentioned ; also a 

 conifer Prototaxites, having spirally-marked cells* 

 characteristic of the genera Taxites and Spiropites of 

 Goeppart, but differing in the cylindrical form and loose 

 aggregation of the wood-cells. Doctor Dawson found 

 in the devonian beds of the State of JSTew York and 

 Canada, thirty-two genera, and sixty-nine species of 

 plants, comprising Bigillatfiafy Calamites, Aster- 

 ophyllites, the Lepidodendron^ conifers and ferns of the 

 genera Cyclopteris, Neuropteris, S]?henoj)teris,alsofrmts, 



