estoration. Portions of _Sphenopteris bifida_, for instance, a
fern of the Lower Carboniferous rocks have been repeatedly figured; but
a beautiful specimen on the table, which exhibits what seems to be the
complete frond of the plant, will give, I doubt not, fresh ideas
respecting the general framework, if I may so speak, of this skeleton
fern, to even those best acquainted with the figures; and an elaborate
restoration of its contemporary, _Sphenopteris affinis_ (see
frontispiece) which I completed from a fine series of specimens in my
collection, will be new, as a whole, to those most familiar with this
commonest of the Burdiehouse fossils. From comparisons instituted
between minute portions of this Sphenopteris and a recent fern, it has
been held considerably to resemble a Davallia of the West Indies;
whereas it will be seen from the entire frond that it was characterized
by very striking peculiarities, exemplified, say some of our higher
botanical authorities, to whom I have submitted my restoration, by no
fern that now lives. The frond of _Davallia Canariensis_, though unlike
in its venation, greatly resembles in general outline one of the larger
pinnae of _Sphenopteris affinis_; but these pinnae form only a small part
of the entire frond of this Sphenopteris. It was furnished with a stout
leafless rachis, or leaf-stalk, exceedingly similar in form to that of
our common brake (_Pteris aquilina_). So completely, indeed, did it
exhibit the same club-like, slightly bent termination, the same gradual
diminution in thickness, and the same smooth surface, that one
accustomed to see this part of the bracken used as a thatch can scarce
doubt that the stipes of Sphenopteris would have served the purpose
equally well; nay, that were it still in existence to be so employed, a
roof thatched with it, on which the pinnae and leaflets were concealed,
and only the club-like stems exposed, row above row, in the style of the
fern-thatcher, could not be distinguished, so far as form and size went,
from a roof thatched with brake. High above the club-like termination of
the rachis the stem divided into two parts, each of which, a little
higher up, also divided into two; these in turn, in at least the larger
fronds, also bifurcated; and this law of bifurcation,--a marked, mayhap
unique, peculiarity in a fern,--regulated all the larger divisions of
the frond, though its smaller pinnae and leaflets were alternate. It was
a further peculiar