418 THE PRIMITIVE VEGETATION OF THE EARTH. 
A second species of Psilophyton (P. robustius), also 
abundant at Gaspé, shows stouter stems than the former, 
more abundantly branching and with smaller leaves, often 
quite rudimentary. Its spore-cases are also of different 
form and borne in dense clusters on the sides of the stem. 
Masses of very slender branching filaments appear to indi- 
cate a third species (P. elegans) which is also found in the 
Devonian of St. John, New Brunswiek. These species of 
Psilophyton occur both in the lower and middle Devonian, 
and, as will be mentioned in the sequel, they extend also 
into the Upper Silurian. 
Decorticated and flattened stems of Psilophyton cannot be 
readily recognized, and except when their internal structure 
has been preserved, might be mistaken for alge, a mistake 
which I believe has in some instances been made. Speci- 
mens of the barren stems (var. ornatum) might readily be 
referred to the genus Lycopodites. 
Another genus of generalized type is that named by 
Haughton Cyclostigma. As found at Gaspé it presents 
slender stems with rounded scars, placed either spirally or 
in transverse rows, and giving origin to long rigid leaves. 
It had a slender axis of scalariform vessels, and fructifica- 
tion of the form of elongated spikes or strobiles is found 
with it. In many respects these plants resemble Psilophy- 
ton, and their affinities were distinctly Lycopodiaceous. 
Specimens from Ireland, in the Museum of the Geological 
Society, kindly shown to me by Mr. Etheridge, appear to 
show that in that country these plants attained the dimen- 
sions of trees, and had roots of the nature of Stigmaria. Mr. 
Carruthers has even suggested that they may be allied to 
Syringodendron, a group of Carboniferous trees connected 
with the Sigillarie. 
The genus Lycopodites is represented by a trailing spe- 
cies, bearing numerous oval strobiles (L. Richardsoni), a 
species quite close to many modern club-mosses (L. Mat- 
thewi), and a remarkable pinnate form (L. Vanuxemit); 
