outline
resemble, as I have said, the fronds of the recent Hart's-Tongue fern
(_Scolopendrium vulgare_), except that their base is lanceolate, not
cordate. Of these last there are two kinds in the beds, representative
of two several species, or, as their difference in general aspect and
detail is very great, mayhap two several genera. The smaller of the two
has a slender midrib, depressed on its upper side, and flanked on each
side by a row of minute, slightly elongated protuberances, but elevated
on the under side, and flanked by rows of small but well marked grooves,
that curve outwards to the edges of the leaf. The larger resemble a
Taeniopteris of the English and Continental Oolites, save that its midrib
is more massive, its venation less at right angles with the stem, its
base more elongated, and its size much greater. Some of the Helmsdale
specimens are of gigantic proportions. From, however, a description and
figure of a plant of evidently the same genus,--a Taeniopteris of the
Virginian Oolite, given by Professor W.B. Rogers of the United
States,--I find that some of the American fronds are larger still. My
largest leaf from Helmsdale must have been nearly five inches in
breadth; and if its proportions were those of some of the smaller ones
of apparently the same species from the same locality, it must have
measured about thirty inches in length. But fragments of American leaves
have been found more than six inches in breadth, and whose length cannot
have fallen short of forty inches. The Taeniopteris, as its name bears,
is regarded as a fern. From, however, the leathern-like thickness of
some of the Sutherland specimens,--from the great massiveness of their
midrib,--from the rectilinear simplicity of their fibres,--and, withal,
from, in some instances, their great size,--I am much disposed to
believe that in our Scotch, mayhap also in the American species, it may
have been the frond of some simple-leaved Cycas or Zamia. But the point
is one which it must be left for the future satisfactorily to settle;
though provisionally I may be permitted to regard these leaves as
belonging to some Cycadaceous plant, whose fronds, in their venation
and form, resembled the simple fronds of Scolopendrium, just as the
leaves of some of its congeners resembled the fronds of the pinnate
ferns.

[Illustration: Fig. 141.]

[Illustration: Fig. 142.]

I have already referred to the close resemblance which certain
Cycadaceous gene