IMAGE EVALUATION TEST TARGET (MT-3) 1.0 I.I 1.25 in 11128 132 I m 2.2 It m III 2.0 1.8 U III 1.6 <9 ^ V2 //, ^m c^. «> % ^>. -^ ^/^^ Photographic Sciences Corporation 33 WEST MAiN STREET WEBSTER, NY. 14580 (716) 873-4503 ^ CIHM/ICMH Microfiche Series. CIHM/ICJVIH Collection de microfiches. Canadian Institute for Historical Microreproductions Institut Canadian de microreproductions historiques 1980 Technical and Bibliographic Notas/Notes techniques et bibliographiques The Institute has attempted to obtain the best original copy available for filming. Features of this copy which may be bibiiographicaiiy unique, which may alter any of the images in the reproduction, or which may significantly change the usual method of filming, are checked below. 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Lorsque le document est trop grand pour Atre reproduit en un seul clichA, il est filmA A partir de Tangle supArieur gauche, de gauche A droite, et de haut en bas, en prenant le nombre d'images nAcessaire. Les diagrammes suivants illustrent la mAthode. 1 2 3 1 2 3 4 5 6 J-^Mk.W^' 'yf»" (^From the Canadian Natimtlist, Vol. X. No. 2.) ', ■.! 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 ^M ■% •••#■' m ^kM I :^M''^ MS 2 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. AM-] 1" T 3 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