Part 17

Assuming the Archæospherinæ so abundantly found in the Eozoon limestones to be distinct organisms, and not mere germs or buds of Eozoon, they may be thus defined:--

Genus Archæospherina, Dawson.

A provisional genus, to include rounded solitary chambers, or globigerine assemblages of such chambers, with the cell-wall surrounding them tubulated as in Eozoon, or perhaps in some cases with simple pores like those of Rotalines. They may be distinct organisms, or gemmæ, or detached fragments of Eozoon. Some of them much resemble the bodies figured by Dr. Carpenter, as gemmæ or ova and primitive chambers of Orbitolites. They are very abundant on some of the strata surfaces of the limestones at Côte St. Pierre. Age Upper Laurentian.

I may add here the characters of Matthew's new genus, Archæozoon, as given by him:--

Genus Archæospherina, Matthew.

Skeleton composed of thin concentric laminæ convex upward, and having between them a granular layer filled with minute branching canals.

Archæospherina Acadiense, Matthew.

Habit of growth cylindrical in masses or groups, budding upward. The microscopic characters are thus given by Matthew:--

"The structures appear to be allied more closely to Cryptozoon than to Eozoon. The microscopic structure is most easily recognised in the earthy (as distinguished from the calcareous) layers, and consists of minute branching canals. Under a one-inch objective the smaller canals have the appearance of minute threads, which run sometimes for a distance of two millimetres without branching. The larger canals branch more frequently and are more sinuous. The canals cross and anastomose with each other; they run chiefly at right angles to the axis of the fossil, and appear to branch most in going outward from the centre. More rarely they ascend from the earthy to the calcareous layer, branching upward."

In limestone of the Upper Laurentian, near St. John, New Brunswick.

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D. Cryptozoon.

The description above given of Archæozoon very naturally leads us to consider the allied Cambrian and pre-Cambrian forms known as Cryptozoon.

This remarkable and problematical type was first described by Prof. James Hall in the Appendix to his Annual Report of 1882 (No. 26). It is a large massive organism, occurring abundantly on the surface of a limestone of Calciferous (Upper Cambrian) age at Greenfield, Saratoga County, New York. The individuals sometimes attain a diameter of two feet, and are often surrounded by smaller specimens apparently budding off from them. Like Stromatoporæ, they consist of concentric laminæ, but these are concave upward, giving a bowl-shaped form to the summits of the individuals. Prof Hall describes them as "made up of irregular concentric laminæ of greater or less density, and of very unequal thickness. The substance between the concentric lines in well-preserved specimens is traversed by numerous minute irregular canaliculi which branch and anastomose without regularity. The central portion of the masses is usually filled with crystalline granular and Oolitic material, and many specimens show the intrusion of these extraneous and inorganic substances between the laminæ."

Professor Hall having kindly presented some good specimens to the Peter Redpath Museum, I have had sections made, and have thus been able to verify his description, and to compare the structures with those of some of the more ancient Stromatoporoid specimens in our collections, including the Archæozoon from New Brunswick, of which Mr. Matthew has presented a fine slab to the Museum. I have also, through the kindness of Professor Winchell, been enabled to compare these with his Cryptozoon Minnesotense, and Dr. Walcott has added specimens of his Stromatoporoid forms from the pre-Cambrian beds of Arizona. It would appear from these and other specimens in our collections from the Cambrian and older Ordovician beds, that we have here an ancient type of Stromatoporoid organism in which the original laminæ seem to have been thin and coriaceous, without apparent pores or pillars connecting them with each other, but having between them relatively-thick layers of fine fragmental matter penetrated by numerous irregularly tortuous and branching tubes. The laminæ often present a carbonaceous or chitinous appearance, though frequently replaced by mineral matter, and the intervening layers show both a calcareous and carbonaceous substance, with much fine silicious sand often as rounded grains, and apparently some dolomitic granules. The tubules seem destitute of any distinct wall, otherwise the whole would resemble on a large scale the nodular and laminated masses of Girvanella, which Wethered has described as surrounding organic fragments in Silurian and Carboniferous and Jurassic limestones in England.

The Streptochetus of Seely from the Chazy limestone is evidently very near to Girvanella, if not generically identical, and I have a similar species from the Lower Cambrian pebbles in the conglomerates of the Quebec group. In all these forms, however, the thicker or intermediate laminæ seem to consist wholly of definite convoluted tubes, whereas in Cryptozoon the tubes, or tubular perforations, are separated by a mass of material which in the best preserved specimens seems to consist of a fibrous stroma including calcareous and silicious particles. It seems doubtful to what class of beings such a structure should be referred; but whatever its nature, it evidently had great powers of growth, and seems to be a very ancient form of life.

One of the species similar in structure to Hall's type, but budding out into turbinate branches, was discovered by Mr. E. T. Chambers, of Montreal, in the Ordovician limestone of Lake St. John, and has been named C. boreale. It differs in structure from Hall's species in having the tubes less tortuous and more nearly parallel to the laminæ. In its outline it reminds one of the problematical Eozoon from the Hastings group at Tudor, Ontario, referred to in the text.

Should time permit, I hope to have all the specimens in our collections illustrating this interesting and primitive type examined and described. In the meantime I may merely remark that a near modern analogue would seem to be the gigantic arenaceous Foraminifer Neusina Agassizi, Goës, dredged by Alexander Agassiz in the Pacific, and described in the Bulletin of the Museum of Comparative Zoology (Vol. xxiii., No. 5, 1892). The modern form, it is true, is flat and foliaceous; but some of the old species approach to this shape, and if we suppose the little cells of Neusina to represent the tubes of Cryptozoon, and the carbonaceous matter of the latter to be the remains of the chitinous stroma seen in some specimens, the general resemblance will be very close.

The whole subject of these peculiar Stromatoporoid forms extending from the Upper Cambrian to the Laurentian, deserves a full and careful investigation, for which I am endeavouring to collect material.

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E. Receptaculites and Archæocyathus.

In "The Dawn of Life" (1875), reference was made to the singular and complicated organisms of the Upper Cambrian and Ordovician systems known as Receptaculites, which at that time was generally regarded as foraminiferal, and is still placed by Zittel, in his great work on Palæontology, among forms doubtfully referable to that group. It has also been referred to Sponges, though on very uncertain grounds. It has not, however, so far as I am informed, been traced any farther back than the Upper Cambrian (Calciferous), and no structural links are known to connect it with either Eozoon or Archæozoon. For this reason it was omitted in the text; but I think it well to mention it here, and to direct attention to it as possibly one of the complex Protozoa which may be traced far back toward the beginnings of life.

Another primitive and generalized genus mentioned in the text is Archæocyathus of Billings, whose headquarters seem to be in the Lower Cambrian, and which may probably be traced farther back.

Mr. Billings described the genus in his "Report on Canadian Fossils" (1861-64), taking A. profundus, from the Lower Cambrian of L'Anse à Loup, on the Labrador coast, in the first instance, as the type.

A few years later, my attention was attracted to this species by specimens presented to me by Mr. Carpenter, a missionary on the Labrador coast, and which Mr. Billings kindly permitted me to compare with his specimens in the Museum of the Geological Survey, collected by the late Mr. Richardson, at L'Anse à Loup, in Labrador, in what were then called Lower Potsdam rocks. Slices of the specimens were made for the microscope, when it appeared that, though they had the general aspect of turbinate corals, like Petraia, etc., they were quite dissimilar in structure, more especially in their porous outer and inner walls and septa (see Fig. 5, p. 35). Yet they could scarcely be referred to the group of porous corals known in much later formations and in the modern seas. Nor could they be referred with much probability to Sponges, as they were composed of solid calcareous plates, which, as was evident from their textures, could not have been originally spicular. One seemed thus shut up to the conclusion that their nearest alliance was with Foraminifera, and if so, they were very large and complex forms of that group, consisting of perforated chambers arranged around a central cavity. I accordingly mentioned them in this connection in 1875, not as closely related to Eozoon, but as apparently showing the existence of very complex foraminiferal forms in the Lower Cambrian.

The specimens thus noticed were altogether calcareous, and were of the species named A. profundus by Mr. Billings. He had, however, referred to the same genus silicified specimens from a later formation, the Calciferous (Upper Cambrian) at Mingan, under the name A. Minganensis, which were subsequently found to be associated with spicules resembling those of lithistid sponges, and which proved to be very different from the Lower Cambrian form, and are now referred to a different genus. The subject had thus become involved in some confusion, and was left in this state by Mr. Billings on his death. I therefore asked my friend, Dr. Hinde, of London, to re-examine my specimens, and at the same time those of the Geological Survey were placed in his hands by Mr. Whiteaves. Hinde also obtained specimens from Lower Cambrian rocks in Sardinia, where they seem to be abundant, and from Spain. He states the results of his examinations very fully in a paper in the Journal of the Geological Society of London. He retains the original name for the older and calcareous form from L'Anse à Loup, separating from it, however, another form, A. Atlanticus of Billings's, which is destitute of distinct radiating septa and acervuline, like the lower part of A. profundus. This he names Spirocyathus. The Mingan species he places with Sponges under the generic name, Archæoscyphia. In this Walcott substantially agrees with Hinde in his "Memoir on the Lower Cambrian Fauna." Both seem to refer Archæocyathus to corals, though admitting its very exceptional and anomalous structure. I think, however, we may still be allowed to entertain some doubts as to the reference to corals, more especially as the skeleton does not seem to have consisted of aragonite, but of ordinary calcite, like that of the Foraminifera. It is in any case a primitive form which seems to be dying out in the Lower Cambrian, and we may hope that it may be traced into the pre-Cambrian, and may form a link connecting the Palæozoic with the Eozoic faunas. In my description of it in "The Dawn of Life" in 1875, I used the following terms:--"To understand Archæocyathus, let us imagine an inverted cone of carbonate of lime from an inch or two to a foot in length, with its point planted in the mud in the bottom of the sea, while its open cup extends upward into the clear water. The lower part buried in the bottom is composed of an irregular network of thick calcareous plates, enclosing chambers communicating with one another. Above this, where the cup expands, its walls are made up of inner and outer plates, perforated with numerous round pores in vertical rows, and connected with each other by vertical partitions also perforated, so as to establish a free communication of the enclosed radiating chambers with each other, as well as with the water within and without. Such a structure might no doubt serve as a skeleton for a coral of somewhat peculiar internal structure, but it might just as well accommodate a protozoan with chambers for its sarcode, and pores for emission of pseudopods, both outwardly and by means of the interior cup, which in that case would represent a funnel like that of Carpenteria, or one of the tubes of Eozoon."

On the whole, when we consider the magnitude and synthetic character of such forms as Cryptozoon, Receptaculites, and Archæocyathus, and their association with generalized types of Crustaceans and Brachiopods, we can scarcely fail to perceive that at the base of the Palæozoic we are leaving the reign of the higher marine invertebrates, and entering on a domain where lower and probably Protozoan forms must be dominant, and so are getting at least within calculable distance of the beginnings of life.

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