oes not seem to have been that of a Cycadaceous
plant, as it occupied evidently not a terminal position on the plant
that bore it, like the cones of Zamia or the flowers of Cycas, but a
lateral one, like the lateral flowers of some of the Cactus tribe.
Another class of vegetable forms, of occasional occurrence in the
Helmsdale beds, seems intermediate between the Cycadaceae and the ferns:
at least, so near is the approach to the ordinary fern outline, while
retaining the stiff ligneous character of Zamia, that it is scarce less
difficult to determine to which of the two orders of plants such
organisms belonged, than to decide whether some of the slim graceful
sprigs of foliage that occur in the rocks beside them belonged to the
conifers or the club mosses. And I am informed by Sir Charles Lyell,
that (as some of the existing conifers bear a foliage scarce
distinguishable from that of Lycopodiaceae), so a recently discovered
Zamia is furnished with fronds that scarce differ from those of a fern.
Even _Zamia pectinata_ may, as Sternberg remarks, have been a fern.
Lindley and Hutton place it merely provisionally among the Cycadaceae, in
deference to the judgment of Adolphe Brogniart, and point out its
resemblance to _Polypodium pectinatum_; and a small Helmsdale frond
which I have placed beside it bears the impress of a character scarce
less equivocal. The flora of the Oolite was peculiarly a flora of
intermediate forms.

[Illustration: Fig. 139.]

[Illustration: Fig. 140.]

We recognize another characteristic of our Oolitic flora in its
simple-leaved fronds, in some of the species not a little resembling
those of the recent Scolopendrium, or Hart's-Tongue fern,--a form
regarded by Adolphe Brogniart as peculiarly characteristic of his third
period of vegetation. These simple ferns are, in the Helmsdale deposits,
of three distinct types. There is first a lanceolate leaf, from two and
a half to three inches in length, of not unfrequent occurrence, which
may have formed, however, only one of the four leaflets, united by their
pseudo-footstalks, which compose the frond of Glossopteris,--a
distinctive Oolitic genus. There is next a simple ovate lanceolate
leaf, from four to five and a half inches in length, which in form and
venation, and all save its _thrice_ greater size, not a little resembles
the leaflets of a Coal Measure neuropteris,--_N. acuminata_. And, in the
third place, there are the simple leaves that in general