66

Henry Steinhauer,* who described it under Martin's name " Phytolithus verrucosus." He supposed it to have been a cylindrical trunk or root growing in a direction nearly horizontal, in the soft mud, at the bottom of freshwater lakes or seas, without branches, but sending out fibres on all sides."

The next account of this fossil appeared in the "Fossil Flora," by Lindley and Hutton, who have expressed themselves much in the same terms as Steinhauer, respecting its habitat and mode of vegetating; but instead of a branchless cylindrical trunk, as Steinhauer supposed, their view is, that it had a centre, in the form of a "continuous homogeneous cup or dome," from which "numerous arms proceeded on all sides."

In connection with the specimen which has led to the foregoing opinion, and which Messrs Lindley and Hutton have figured in their "Fossil Flora," † a point must, in the next place, be considered, which, if not cleared up, will leave the question now entered upon completely inconclusive, however cogent the arguments may be that are to be adduced.

As the specimen itself has not been fully described,—and as it is fortunately preserved in the Newcastle Museum, though not exactly in the same condition as when first obtained,-the present opportunity may be embraced to state, that it is a convex mass of shale about four feet and a-half in diameter, and fifteen inches high in the centre: the crown or central part, which may be reckoned two feet across, is evenly rounded, and the sides are channelled: the whole of the crown is crowded with strongly marked wrinkles, which pass off into the channels on the sides: in a few instances, a channel is occupied with a compressed branch, also composed of shale, and encircled with a thin layer of coal-in this case, the remains of a cuticle; with this exception, the specimen is completely decorticated. It is necessary to observe, that the strong wrinkles of the crown become much finer as they pass off into the channels; and that there is superadded to the latter a number of scars, which, as well as their accompanying wrinkles, are in every respect similar to those of Stigmaria: both characters were doubtlessly impressed by the outer surface of the cuticle of the branches. After alluding to some other specimens which had been discovered in the roof of the Bensham seam in Jarrow colliery, one of which is described as shewing a central concavity and fifteen arms proceeding from it, and consequently resembling the fossil represented in their thirty-first plate, figure 1, the authors of the "Fossil Flora," proceed to state, that the convex specimen "has detached itself from the roof, which none of the before-cited instances did. This exhibits the same wrinkled appearance, with indistinct circular spots, as the under side, described vol. i.

Transactions of the American Philosophical Society, N. S. Vol. i. 1818. "Fossil Flora," vol. ii. Preface, p. xiii.

page 104; it has nine arms, five of which subdivide into two branches, at about eighteen inches from the centre of the fossil, and one at three feet; in this, as in the other instance, they are all broken off short."* But the branches-what connection have they with the specimen upon which they rest? This is a question that does not appear to have been sufficiently attended to when drawing up the description just quoted. From the remark elsewhere made, that Stigmaria was "of a yielding fleshy substance, with numerous arms, proceeding on all sides from a central dome," one would be induced to suppose that the "arms" of the convex specimen grew out from the margins of the "central portion." I cannot agree to this, because the specimen affords no evidence in support of it: on the contrary, nothing is more easy to prove, than, that the arms or branches had no other connection with the specimen but that of superposition. The proving of this may be effected by simply removing the branches, when it will be seen that the markings on the channels are perfectly continuous with the wrinkles on the central portion: were it as is generally supposed, the wrinkled part would here and there display a fractured surface, arising from the breaking off of the branches.

From what has just been said, it is evident that the markings on the central portion of the convex specimen have been produced in the same manner as the scars and wrinkles on the channels; or, in other words, that they are merely impressions which have been derived from a superimposed body: in short, it follows, that this specimen is nothing more than an indurated mass of mud, precisely similar to what must have occupied the hollow or under surface of the fossil represented in plate 31, fig. 2, of the "Fossil Flora;" and, that the branches are portions of a Stigmaria which originally rested upon it, and which probably still remains fixed in the roof of the pit.

The explanation which has been given, there is every reason to suppose, would not have been required, but for the fact, that the branches have undergone so much compression, especially at their upper extremity, as to produce the appearance as if they had grown out from the sides of the specimen, and as if the markings on their upper surface were continuous with the wrinkles on the crown. I am fully persuaded, it is entirely through this deceptive appearance that Lindley and Hutton have been led into the belief that Stigmaria had a domeshaped centre, from which numerous arms procceded on all sides. Agassiz also appears to have been misled in the same manner.‡

Another point remains to be disposed of. From the "ideal vertical section," which is given in plate 31, figure 2, of the "Fossil Flora,” it might be concluded that Stigmaria had a rounded or convexly formed upper surface The untenableness of this conclusion will, however, be

• "Fossil Flora," vol. ii. preface, pages xiii. and xiv. Translation of the "Bridgewater Treatise." VOL. XXXVII. NO. LXXIII.-JULY 1844.

† Ibid. p. xv.

E

manifest from the fact, that, up to the present time-although I have now examined several specimens-I have not fallen in with one which exhibits the upper surface otherwise than truncated: further, when the centre of a Stigmaria has fallen from the roof, a portion in the shape of a stem, and answering to the truncated surface, is often seen remaining in the roof, and passing upwards.*

The disposal of these two points (and they have, I am decidedly of opinion, been the greatest hinderances to the working out of the true character of this fossil), not only proves, that the prevailing opinion regarding the form of Stigmaria is erroneous, but it leads to the inference, that what has hitherto been looked upon as the centre of this fossil, is in the form of a root stock deprived of its stem.

All the specimens of Stigmaria which have been seen in a perfect condition, or nearly so, have their branches running out in the manner of wide-spreading roots: this will be sufficiently evident by consulting figure 1, plate 31, of the "Fossil Flora." Besides the specimen just referred to, several others are still to be seen fixed in the roofs of several pits in this district. At Felling, a very large specimen occupies the roof of one of the galleries: it is impossible to ascertain its size, as it passes into an unworked part of the mine: some of the branches, at a little distance from their commencement, measure eighteen inches across in the compressed state. An idea may be formed of the dimensions which some Stigmarias attain, from the statement communicated to me by the head wasteman of Felling pit, that he has traced the impression of a single branch for full fifty feet, without finding its terminations. I am quite disposed to credit this statement, for I myself have measured an impression of this fossil in the roof of Jarrow pit, and succeeded in following it for thirty feet, until it disappeared in a part where the workmen had not carried on their operations. And, very lately, I have obtained for the Newcastle Museum, portions of three different specimens, equally confirmatory of the immense size which some Stigmarias attain. The first is a branch fifteen feet in length, rather flexuose, and remarkably uniform in thickness, which is four inches. The second differs from the last in being singularly yet gracefully tortuous, and in diminishing at one end to a mere film; the opposite end appears to have been joined to the main body of the fossil; or, what is more probable, this specimen may have been one of the off-sets of a divided branch; it is eleven feet long, and five inches in thickness, at the largest end. The third consists of three furcated branches, which have been broken off from the central stock; the two off-sets of one of these furcated branches are respectively seven and two feet long, and

* In general, these perpendicular stems are so polished or slickensided, that it is impossible to identify them with any known fossil: and nothing is more common than to see the surface of a so-called centre of Stigmaria as smooth as glass. The last is called a "kettle bottom" by the miners. I would suggest that this phenomenon has been produced by the fossil offering some resistance to the enormous compression into which the surroundingg rock has been subjected.

both are truncated. This specimen is by far the finest that has ever been procured in this district; and it appears, from its superficial characters, to be specifically distinct from Stigmaria ficoides. These characters will be reverted to in another part of this paper.

All the specimens of Stigmaria which have been described as occurring in the pits of this district are in the roof, and consequently only their under side is exhibited. There is a very large decorticated specimen, however, in the Ouse Burn, about two miles from Newcastle, having its upper side exposed. When discovered, the part which answers to the stock or centre was visible; and from all that I can ascertain, both from the fragments still remaining, and a sketch made at the time by Mr Albany Hancock, who was the first to make the specimen known, this part was broken in such a manner as to induce the supposition that a stem had been originally attached to it. The only external character which was displayed on the surface of so much of the branches as was visible at the time of the discovery of this fossil, consisted of a number of rude flutings, which character was the cause of some supposing it to be the branched apex of a Sigillaria: it was further supposed, that the stem had been destroyed or removed; and, that the apex, by some means or other, had been overturned, and afterwards covered up with sediment-now an argillaceous sandstone. The complete absence of scars was also appealed to as confirmatory of its belonging to the lastnamed genus, since decorticated specimens of Sigillaria are occasionally to be met with, divested of this character.

This allusion to the Ouse Burn fossil, makes it necessary for me to mention, that, on May the 17th, 1841, and shortly after the Newcastle Museum had become possessed of the earliest received North Biddick Sigillaria, I read, at a meeting of the Natural History Society of Northumberland, Durham, and Newcastle-upon-Tyne, a paper which gave an account of the last specimen, and which adverted to a character occurring on the under side of its base," apparently leading to the conclusion, that Stigmaria is the root of Sigillaria."

The reading of this paper having brought before Mr Hutton, who was present, a question which had often occurred to him, he kindly drew my attention to the Ouse Burn fossil, as likely to assist me in my future researches. A few days afterwards, we examined this fossil, when I became convinced that it was not the branched apex of a Sigillaria, but the central stock of a Stigmaria. Mr Hutton having some doubts on this point, but being anxious to have it settled, he empowered me to employ some workmen to lay bare the branches; and, with his accustomed liberality, he went to considerable expense in the prosecution of this object. Two of the branches were exposed for upwards of six feet, and both were seen to divide, and to dip into the rock at an angle of 40 degrees to the line of stratification: the flutings were observed to become more and more indistinct as they passed downwards; but still no scars were visible. This was the result of our first inspection. I confess, that at this stage of the inquiry, the opinion I had formed was almost forsaken.

However, the idea occurred to me to examine the rock which the workmen had removed, especially those portions which had been in immediate contact with the fossil: this immediately led to the discovery of the cuticle adhering to those portions, in the condition of a rotten carbonaceous layer, which, on being removed, shewed the wrinkles and scars of Stigmaria. Nor was this all; the appendages were seen to be attached to wherever the scars were visible, and to penetrate the rock in regular directions. Thus, the evidences as to the fossil being a Stigmaria were conclusive; and it may be added, that the running out of its branches, in the manner of wide-spreading roots, was placed beyond dispute.

The well-known appendages, so often seen attached to the branches of Stigmaria, have, in general, been looked upon as leaves. They are nearly always flattened; occasionally, however, they are observed to be round, or, rather, vermicular—thus reminding one of the fibrils of the yellow water lily (Nuphar lutea); and there is little doubt, from the form of the scars which they leave when detached, that they were of this form originally. A beautiful and instructive example, shewing the appendages completely vermicular, has been figured by Sternberg.*

Steinhauer says, he found traces of these appendages proceeding from a branch" in every direction, to the distance of 20 feet,”-a statement which Lindley and Hutton think has originated through some error of observation, since they have never been able to trace them to a distance of more than 3 feet; but, it would appear, from the researches of Mr Logan, in the coal-mines of South Wales, that the length which Steinhauer gives to the appendages is not at all exaggerated,—the former having "traced them in a vertical direction, 7 or 8 feet from the stem, and more than 20 feet horizontally." Up to the present time, I have never seen them exceed 18 inches.

Artis in his "Antediluvian Phytology," represents the appendages as forked. I cannot say whether this character has been observed by any other observer. Once I saw an appearance of the kind; but still I cannot urge it with any degree of confidence.

One of the most important circumstances connected with the appendages, is the regular manner in which they are arranged around the branch to which they are attached. Steinhauer appeals to this circumstance as a proof that Stigmaria was a root which grew at the bottom of fresh water lakes, and which "shot out its fibres in every direction through the then yielding mud."§ The following extract from the "Fossil Flora" is to the same effect:-"The leaves also, which thickly surrounded the arms, could not, under any circumstances, even sup

"Flore du Monde Primitif," Parts 5 and 6, Tab. xv., fig. 4.

↑ Buckland's Anniversary Address to the Geological Society, delivered in 1841, page 34.

+ Plate III.

"Transactions of the American Philosophical Society," N. S., Vol. i., p 273.