England, published a description of the Tasmanite and Australian white coal, in which he shows that the organisms in these deposits are similar to my Sporangites Huronensis, and to the macrospores previously described by Prof. Huxley, from the Better-bed coal. Mr. Newton does not seem to have been aware of my previous description of Sporangites, and proposes the name Tasmanites punctatus for the Australian form. Here we have the remarkable fact that the waste macrospores, or larger spores of a species of Cryptogamous plant, occur dispersed in countless millions of tons through the shales of the Erian in Canada and the United States. No certain clue seemed to be afforded by all these observations as to the precise affinities of these widely distributed bodies; but this was furnished shortly after from an unexpected quarter. In March, 1883, Mr. Orville Derby, of the Geological Survey of Brazil, sent me specimens found in the Erian of that country, which seemed to throw a new light on the whole subject. These I described and pointed out their connection with Sporangites at the meeting of the American Association at Minneapolis, in 1883, and subsequently published my notes respecting them in its proceedings, and in the "Canadian Record of Science." Mr. Derby's specimens contained the curious spiral sea-weed known as Spirophyton, and also minute rounded Sporangites like those obtained in the Erian of Ohio, and of which specimens had been sent to me some years before by the late Prof. Hartt. But they differed in showing the remarkable fact that these rounded bodies are enclosed in considerable numbers in spherical and oval sacs, the walls of which are composed of a tissue of hexagonal cells, and which resemble in every respect the involucres or spore-sacs of the little group of modern acrogens known as Rhizocarps, and living in shallow. water. More especially they resemble the sporocarps of the genus Salvinia. This fact opened up an entirely new field of investigation, and I at once proceeded to compare the specimens with the fructification of modern Rhizocarps, and found that substantially these multitudinous spores embedded in the Erie shales may be regarded as perfectly analogous to the larger spores of the modern Salvinia natans of Europe, as may be seen by the representation of them in Fig. 16. FIG. 16.-Sporangites (Protosalvinia). A, Sporangites Braziliensis, natural size. Ax, Same, magnified. B, Sp. biloba, natural size. c, Detached macrospores. D, Spore-cases of Salvinia natans. DX, Same, magnified. E, Shale with sporangites, vertical section, highly magnified. The typical macrospores from the Erian shales are perfectly circular in outline, and in the flattened state appear as discs with rounded edges, their ordinary diameter being from one seventy-fifth to one one hundredth of an inch, though they vary considerably in size. This, however, I do not regard as an essential character. The edges, as seen in profile, are smooth, but the flat surface often presents minute dark spots, which at first I mis took for papillæ, but now agree with Mr. Thomas in recognising them as minute pores traversing the wall of the disc, and similar to those which Mr. Newton has described in Tasmanite, and which Mr. Wethered has also recognised in the similar spores of the Forest of Dean shales. The walls also sometimes show faint indications of concentric lamination, as if they had been thickened by successive deposits. As seen by transmitted light, and either in front or in profile, the discs are of a rich amber colour, translucent and structureless, except the pores above referred to. The walls are somewhat thick, or from one-tenth to onetwentieth the diameter of the disc in thickness. They never exhibit the triradiate marking seen in spores of Lycopods, nor any definite point of attachment, though they sometimes show a minute elongated spot which may be of this nature, and they are occasionally seen to have opened by slits on the edge or front, where there would seem to have been a natural line of dehiscence. The interior is usually quite vacant or structureless, but in some cases there are curved internal markings which may indicate a shrunken lining membrane, or the remains of a prothallus or embryo. Occasionally a fine granular substance appears in the interior, possibly remains of mi crospores. The discs are usually detached and destitute of any envelope, but fragments of flocculent cellular matter are associated with them, and in one specimen from the corniferous limestone of Ohio, in Mr. Thomas's collection, I have found a group of eight or more discs partly enclosed in a cellular sac-like membrane of similar character to that enclosing the Brazilian specimens already referred to. The characters of all the specimens are essentially similar, and there is a remarkable absence of other organisms in the shale. In one instance only, I have observed a somewhat smaller round body with a dark centre or nucleus, and a wide translucent margin, marked by a slight granulation. Even this, however, may indicate nothing more than a different state of preservation. It is proper to observe here that the wall or enclosing sac of these macrospores must have been of very dense consistency, and now appears as a highly bituminous substance, in this agreeing with that of the spores of Lycopods, and, like them, having been when recent of a highly carbonaceous and hydrogenous quality, very combustible and readily admitting of change into bituminous matter. In the paper already referred to, on spore-cases in coals, I have noticed that the relative composition of lycopodium and cellulose is as follows: Cellulose, C24H20020. Thus, such spores are admirably suited for the production of highly carbonaceous or bituminous coals, etc. Nothing is more remarkable in connection with these bodies than their uniformity of structure and form over so great areas and throughout so great thickness of rock, and the absence of any other kind of spore-case. This is more especially noteworthy in contrast with the coarse coals and bituminous shales of the Carboniferous, which usually contain a great variety of spores and sporangia, indicating the presence of many species of acrogenous plants, while the Erian shales, on the contrary, indicate the almost exclusive predominance of one form. This contrast is well seen in the Bedford shales overlying these beds, and I believe Lower Carboniferous.* Specimens of these have been kindly communicated to me by Prof. Orton, and have been prepared by Mr. Thomas. In these we see the familiar Carboniferous spores with triradiate markings called Triletes by Reinsch, and which are similar to those of Lycopodiaceous plants. Still more abun * According to Newberry, lower part of Waverly group. dant are those spinous and hooked spores or sporangia, to which the names Sporocarpon, Zygosporites, and Traquaria have been given, and some of which Williamson has shown to be spores of Lycopodiaceous plants.* The true "Sporangites," on the contrary, are round and smooth, with thick bituminous walls, which are punctured with minute transverse pores. In these respects, as already stated, they closely resemble the bodies. found in the Australian white coal and Tasmanite. The precise geological age of this last material is not known with certainty, but it is believed to be Paleozoic. With reference to the mode of occurrence of these bodies, we may note first their great abundance and wide distribution. The horizontal range of the bed at Kettle Point is not certainly known, but it is merely a northern outlier of the great belt of Erian shales referred to by Prof. Orton, and which extends, with a breadth of ten to twenty miles, and of great thickness, across the State of Ohio, for nearly two hundred miles. This Ohio black shale, which lies at the top of the Erian or the base of the Carboniferous, though probably mainly of Erian age, appears to abound throughout in these organisms, and in some beds to be replete with them. In like manner, in Brazil, according to Mr. Derby, these organisms are distributed over a wide area and throughout a great thickness of shale holding Spirophyton, and apparently belonging to the Upper Erian. The recurrence of similar forms in the Tasmanite and white coal of Tasmania and Australia is another important fact of distribution. To this * Traquaria is to be distinguished from the calcareous bodies found in the corniferous limestone of Kelly's Island, which I have described in the "Canadian Naturalist as Saccamina Eriana, and believe to be Foraminiferal tests. They have since been described by Ulrich under a different name (Mallerina: contribution to "American Palæontology," 1886). See Dr. Williamson's papers in "Transactions of Royal Society of London." |