Note on a fern associated with Platephemera antiqua, Scudder [microform]

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(^From the Canadian Natimtlist, Vol. X. No. 2.)

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Note on a Fern associated with Platephemera An-
TiQUA, Scuddcr. By J. W. Dawson, L.L.D., F.R.S., ^c.

The oldest remains of insects known to geologists, those of the
Brian (Devonian) shales of St. John, New Brunswick, occur in
beds rich in plant remains. It was indeed solely by means of
the extensive quarrying operations carried on by Messrs. Hartt
and Matthew in these beds in search of fossil plants, that the
insect remuius wore discovered. In less thoroughly explored
beds, fossils so rare and so obscure could not have beer found.
It is natural therefore that fossil plants should occur on the
same slabs with the insects. On one of tiicse, holding a frag-
ment of the wing oi' Flatcphcmcra antujua, there appears a con-
siderable portion of a frond of Pecopteris (^Aspiditcs) serndata,
Hartt, a common species in these beds, and also a smi.U frag-
ment of a leaf of the still more common Cordnites liohbll. It
appears that Dr. Geinitz of Dresden saw this specimen in 1866,
and not being at that time familiar with the ferns of the De-
vonian of New Brunswick, very naturally supposed that the
frond was that of the closely allied I*, jdumosn of Brongniart,
and on this ground he was induced to liint a suspicion that the
specimen was of Carboniferous age. Dr. Scuddcr referred to
this opinion of Geinitz in his paper on Devonian insects in the
Geological Magazine, Vol. V. ; and gave reasons sustaining the
Devonian age of both fern and insect. I did not think it neces-
sary to refer publicly to the matter, but took occasion to explain
the true state of the case in a private letter to Geinitz ; and in
my report on the Devonian plants of Canada I quoted Hartt's
description in full, and noticed the distinctness of his species
from P. plumosa .

I find, however, that this doubt ht'.s been revived by Dr. Hagen
in a paper on Devonian insects in the Bulletin of the Museum of
Comparative Zoology for the present year (Vol. viii. No. 14).
Dr. Hagen does not profess to be an authority in fossil plants,
but fortifies his statements by a letter from Mr. Lesquereux,
which does not however touch the question at issue, as he does
nut appear to have compared the specimen or Hartt's species with

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P. plumogn ; and thoujrh he insinuates a doubt as to the validity
of some of nay Devonian species, even this does not apply, since
the species in question was carefully described by the late Prof.
Hartt, and accepted by me after study of his material, which
included several very considerable portions of well-preserved
fronds.

Thouf^h doubts and suspicions thus cast on work carefully and
exhaustively done, in so far as material exists, should not seri-
ously affect the minds of naturalists, I have thought it desirable
to set the matter at rest, as far as possible ; and have therefore,
through the kindness of Dr. Scuddcr and the Curator of the
Boston Society of Natural History, obtained access to the origi-
nal specimen, and would now state the actual facts.

The fern on the specimen in question (No. 849t) of the Boston
Society's collection) is undoubtedly Pecopteris soruhita of Hartt,
and exhibits in a tolerable state of preservation six secondary
pinnae of one side of a primary pinna of the species. To a hasty
observer, supposing the specimen to be a piece of Carboniferous
shale, it would be natural to refer the fern to P. plumosa of
Brongniart or to Aspnlites silesuicus of Goepport, whicli it per-
haps more closely resembles ; and since its fructification is still
unknown, it may quite as likely belong to the group or sub-genus
Aspidites in which Goeppert and Schimper place P. sUesiaca, as
to that of Cyathites in which Schimper places P. plumosa.

The distinctive characters indicated by Hartt are principally
the form and insertion of the pinnae, the slender crenulate revo-
lute, lanceolate pinnules, and the simple veinlets. Perhaps the
most obvious characteristic is the peculiarly elongated acuminate
points of the primary and secondary pinnae, in which this species
seems to differ from all its near allies. In the specimen in ques-
tion, though only a portion of one side of a primary pinna is
seen, and its characteristic elongate termination is absent, yet
one of the secondary pinnae shows this character very well, and
the simple veins and crenate revolute margins may be made out
with a lens in a good light. I do not think that any palaeobo-
tanist, in view of these characters, would decide to identify this
fern with P. plumosa, unless indeed he were of opinion that the
whole group to which that species belongs should constitute one
broad specific type extending from the Devonian to the Permian,
a view to which I should have no objection, provided sufficient
connecting; links can be found.

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It is farther to be observed that this fern occurs with a group
of species which I have shown to be distinct not only from those
of the Coal Formation but from those of the Millstone Grit and
those of the Lower Carboniferous Coal-measures or Hortou series
(sub-Carboniferous of some American geologists), which sub-
floras arc well developed in the Acadian provinces, and overlie
stratigraphically the beds holding the fern which is the subject
of this note and its associated fossils.

I may add here Hartt's description of the plant and my note
on it, from my Report of 1870 : —

^'PeCOPTERIS (AsPIDITES ?) SERRULATA, Hartt. — (PI. XVIII,
Figs. 207 to 209.)— Acad. Geol. p. 553, Fig. 1)2.— M.D.,
St. John, New Brunswiek."
Tripinnate ; pinna short, alternate, close or open, lanceolate,
very oblique, situated on a rather slender, rounded, sub-
flexuose rachis ; pinnules small, linear lanceolate, crenulate,
rcvolute, moderately acute, oblique, sessile, decurrent, widest
at the base, open, separated from one another by a space
ecjual to the width of a pinnule, slightly arched towards the
point of pinna ; longest at base of pinna, decreasing thence
gradually to the apex ; terminal pinnule elongated. Median
nerve entering the pinnule very obli(juely, floxuous, running
to the apex. Nervules very few, obli(jue, simple, and .some-
what rarely forking at the margin."

"Numerous additional specimens of this species confirm Prof.
Hartt's determination of its distinctness from P.pUnnos<i, Brongt.
It perhaps more strongly resembles Goeppert's F. S'desinai ; but
this last has broader nnd more closely arranged pinnules decur-
rent on the petiole. It may be taken as a Devonian representa-
tive of the delicate Pecopterids of which the species above named
are Carboniferous typos. Mr. Hartt's specimens enable me to
represent its habit of growth. Schimpor (, tes under this name
a Carboniferous species of Lesquereux. But Lesquareux's species
is Alethoptf/ris scrruld," (This was subse(|ueutly corrected by
Schimper in the Supplement to his Palteontologie V(^getale.)