SYNCYCLONEMA MEEKANA, Whiteaves.

This species, which was originally described from specimens collected by Mr. Richardson at the Queen Charlotte Islands, has since been recognized in the Lower Cretaceous of Jackass Mountain, also between Fountain and Lilloet, and near the thirty-sixth mile-post on the wagon road to Yale-all localities on the Lower Fraser River.

X.-Illustrations of the Fauna of the St. John Group.

By G. F. MATTHEW, M.A.

(Read May 25th, 1882.)

No. 1. THE PARADOXIDES.

Their History.

Two decades have now elapsed since the discovery of trilobites in the slates near the city of St. John, New Brunswick, Canada. The preliminary notice of these fossils by the late Professor C. F. Hartt appeared in the report of the geological survey of New Brunswick (1865) carried on under Prof. L. W. Bailey, and descriptions of the species appeared a little later in Principal Dawson's "Acadian Geology" (1868). Since that time the structure of the region in which these fossils were found has been worked out by officers of the Geological Survey of Canada, so that the conditions under which the primordial fauna existed in Acadia are now better known than when the first explorations were made. The knowledge of the geological structure of the region, thus acquired, is embodied in various reports of the Geological Survey, and especially in those of 1870-1 and 1878-9, and the map which accompanies the latter report.

From these reports and from the map it will be seen that the strata of the St. John group fill a number of narrow, trough-like basins, lying between the Bay of Fundy and the central Carboniferous area of New Brunswick. Of these basins, that on which the city of St. John is situated is the most important, and it is here also that the life of the period can be studied to the best advantage. The St. John basin lies diagonally across the ridges of Huronian rock that are found in the eastern part of St. John county; and touches the ridge of Laurentian rocks that divides this county from King's. As might naturally be expected the coarser sediments found at the base of the St. John group are largely derived from those older rocks, chiefly the Huronian; and the line of division between it (the St. John group) and the Huronian Formation is marked by conglomerates of mechanical origin which shew no trace of the hardening process by which the Huronian conglomerates and breccias have been so firmly cemented.

The conglomerates of the St. John group are most fully developed in the eastern part of the St. John basin, under the lee of the high ranges of Huronian hills which exist in that direction. In Portland and the city of St. John, at the western end of the basin the following section represents the succession of members in this group in ascending

order :

Beyond Division 5 the beds are supposed to be repeated by an overturn, and have a width across nearly vertical measures of 3000 feet. Owing to this folding of the measures there is some uncertainty as to where the summit of the formation is, and the section given may not include the whole series of deposits. The fauna of Divisions 2 and 5 are very imperfectly known, but there are much larger species of linguloid shells in these divisions than in Division 1; and the orthids of Division 5 are different from Orthis Billingsi of Division 1.

The conglomerate at the base of the St. John group marks the time when the sea of the Acadian epoch invaded the valleys of the Huronian formation near St. John. No trace of life has yet been found in these coarse sediments, nor in the red and green slates into which they pass. After the coloured mud of which these slates are composed was deposited an abrupt change took place in the character of the deposit, and white sands were evenly spread over the whole basin. It is in the upper part of these sands that one meets with the earliest traces of primordial life. These first forms are linguloid shells of several genera. Such shells become more abundant in the upper part of the white and grey sandy beds, and were evidently littoral species, as on tracing the sandstones westward for half a mile they are found to change into a grey slaty and pebbly deposit,-evidently an old beach line-and finally disappear.

Probably the physical condition of the St. John basin at this early period was unfavorable to the growth of the trilobites; but the land was sinking and an additional depth of water in this sheltered area soon encouraged the growth and multiplication of the crustacean fauna. As the sediment which settled from the sea-water in this deepening bay became finer, the remains of marine animals were preserved in greater numbers and variety, so that in the layers of fine slate in group c. of Division 1, many genera characteristic of the early Cambrian age are found.

In group d, the slaty mass becomes quite fine and dark colored, but near St. John,

is much affected by slaty cleavage, and the fossils are so much distorted, especially in the upper part, as to be unrecognizable.

In the beds of Division 2, a return of littoral conditions, and the influx of sand, interfered with the prosperity of the crustacean fauna, and as in the lower sand beds of Division 1., linguloid shells become the prevailing fossils. The Paradoxides which I will describe in this article, are those of the intermediate mud-beds, now converted into a mass of slaty rock (Division 1c).

Trilobites were first found in this formation by Rev. C. R. Matthew, in 1862, at Coldbrook, five miles N. E. of St. John, but these specimens were so much distorted by slaty cleavage as to be barely recognizable as trilobites. Specimens, however, were subsequently found near St. John, in the same band of slates, but in a much better state of preservation. Owing to a misapprehension on the part of the late Professor F. C. Hartt as to the locality from which these fossils came, the species when described by him were accredited to Coldbrook, whereas they were really found within the limit of the town of Portland, just northward of St. John.

These collections, with those of the Geological Survey of New Brunswick (1864), supplemented by a collection made by Prof. Hartt's father, J. W. Hartt, in the following year, formed the material from which Prof. Hartt described the species peculiar to this formation. A preliminary notice of these fossils was published in Dr. L. W. Bailey's report on the geological survey of New Brunswick (Fredericton, 1865), and it was shown that they were equivalent to the primordial fauna of Bohemia; but the full descriptions of the species did not appear at that time. These were given subsequently in the new edition (1868) of the Acadian Geology, by Dr. J. W. Dawson. The forms described by Prof. Hartt were Conocephalites (Conocoryphe), 14 species; Agnostus, 2 species; Microdiscus, 1 species; Paradoxides, 1 species; Lingula, 1 species; Obolella, 1 species; Orthis, 1 species; Discina, 1 species; and (by the late Mr. E. Billings) Eocystites, 1 species. Prof. Hartt's engagements in the United States and his explorations in Brazil, whither he finally transferred himself after his appointment as director of the Geological Survey of that country, prevented him from giving any further attention to the geology of this region; and from the time of the publication of his species in the Acadian Geology, but little has been added to our knowledge of the fauna of the St. John group.

Collections made from time to time during the progress of the Canadian geological survey in New Brunswick, were examined by the late Mr. Billings, palæontologist to the survey, and among these were found fragments of Elliptocephalus and Salterella, and remains of two species of Hyolithes. Beside these, there are the supposed plant remains Palæophycus, Eophyton, etc., of the higher divisions of the St. John group, to which I need not refer further in this connection.

In the spring of 1877, I made large collections of material from this formation with the intention of studying its fauna, but these were destroyed in the disastrous fire which swept over the city of St. John in the summer of that year. I have since renewed these collections in part, and the following article describes the remains of Paradoxides found in the materials collected in these later years.

Conditions under which the fossils are found.

One great obstacle to the study of the organic remains of these ancient rocks is the Sec. IV., 1882. 12

universal prevalence of slaty cleavage. This in most cases has distorted and obscured the fossils of the finer beds of the formation and, indeed, obliterated them entirely in the greater part of the fine slates. It is only lately that I have been able fairly to appreciate the wholesale destruction of organic forms affected through this agency.

During the extensive excavations that were made for the foundations of buildings in the principal streets of St. John, during the two years after the great fire of 1877, large quantities of fine black slate were removed, in which no trace of a fossil could be seen. But scattered at intervals through some of the bands of this slate there were hard compact masses of rock which, when broken, were found to be packed with fossils. The spherical and elliptical masses, which varied in size from about a yard in diameter to nodules of one inch across, had the appearance of imbedded boulders, but the fossils in them were always parallel to the stratification, and similar fossils were subsequently found in irregular beds and lenticular bands of hard rock. In the boulder-like masses there were numerous layers loaded with organic remains, which extended without diminution in the number of the fossils to the very edge of the block, where they suddenly disppeared, and not a trace of them could be found in the adjoining slate rock. The explanation of this curious fact seems to be that in the hard lump there was sufficient carbonate of lime to resist the molecular movement which produced slaty cleavage in the surrounding portion of the deposit, and thus to preserve the fossils from destruction.

There are three great bands of black slates in the mass of the Saint John group on which the city is built, but which, owing to their softness, seldom appear at the surface, and it is highly probable that these bands originally abounded in organic remains. Such having been the destructive action of slaty cleavage on the Cambrian organisms of this district, the rarity in the finer sediments of fossils in a good state of preservation can be better understood. It is necessary to seek over large areas for such, and as a rule they have been found only near the base of the formation.

Of all the genera of trilobites of the Saint John group Paradoxides appears to be that which has suffered most from the distortion due to the movement which produced slaty cleavage in the clay slates. Their tests were more flexible than those of the other genera, and their comparatively large size makes it more difficult to obtain specimens which will show the whole buckler (or even a considerable part of it) in a good state of preservation. The remains of this genus usually resemble crumpled fragments of grey or brown paper, laid irregularly one over the other, without any recognizable shape. When they are not too much crumpled and have their broadest surface parallel to the cleavage planes of the clay-slate they can generally be identified; but the fossils are almost always at an angle with the cleavage, and are also more or less distorted diagonally to the axial line. Even when in the best state of preservation in the argillaceous matrix they are flattened by pressure and the tests cracked and mis-shapen. All these accidents of preservation, except the vertical flattening, have been allowed for in the drawings accompanying this article. In a few cases specimens have been obtained which have been preserved from distortion by a large amount of carbonate of lime in the particular part of the layer in which they occurred, and in these original form of the organism has been more accurately preserved.

The principal fossiliferous zone of the St. John group contains the exuviæ of many generations of trilobites, and probably those of several stages of growth of the same individual. Being a repository of the discarded clothing of many a living trilobite, as well as