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valve of Dithyrocaris? most beautifully sculptured, of which the following is a description. The specimen is eleven lines in breadth, and probably measured, when entire, nearly two inches in length. The dorsal border is rounded in a corresponding degree with the ventral border; a small rostrum is observable at the anterior end, from which two prominent ridges also take their rise and pass over the side, one arching towards the dorsal, the other bending towards the ventral line, but uniting again on the centre of the valve at one inch from the anterior end. The fine striæ above and below these prominent ridges are parallel, but those inclosed in the central elliptical space cross one another so as to form a finely reticulated pattern on its surface. The eye spot is distinct and prominent at the anterior end, near the intersection of the two curved ridges. Other slight, scarcely visible, folds traverse the carapace parallel to the ventral and dorsal border, indicating that the original shell was of extreme tenuity, like that of the recent Apus and Estheria.

Should the discovery of other and more perfect specimens prove this to be a true Dithyrocaris, it will be the first specimen of this genus met with in rocks of Devonian age.

I had proposed to call this form D. striatus,* but as there is already a D. tenuistriatus, it will be better not to give it so indistinct a name. I therefore beg to name it Dithyrocaris? Belli, after its discoverer.

THE POST-PLIOCENE GEOLOGY OF CANADA. By J. W. DAWSON, LL.D., F.R.S., F.G.S. Introductory.

When in 1855 the writer, in consequence of accepting the office of Principal of McGill College, was removed from the Carboniferous Districts of Nova Scotia, and thus to some extent debarred from the prosecution of his researches in the carboniferous rocks of that Province and their fossil plants, he determined, with the advice of Sir W. E. Logan, then Director of the Geological Survey of Canada, to take up as an occasional pursuit the study of the Drift Deposits of Canada, a work which had, at

• British Association Reports, Section C., Liverpool, 1870.

least, this link of connection with previous occupations, that it related in part to marine animals, with which his Zoological studies on the sea coast had made him familiar.

The results of these studies have, in part, been published in the following papers:—

(1.) On the Newer Pliocene and Post-Pliocene of the Vicinity of Montreal.-Canadian Naturalist, 1857.

(2.) Additional Notes on the Post-Pliocene Deposits of the St. Lawrence Valley.-Ib. 1859.

(3.) On the climate of Canada in the Post-Pliocene Period.Ib. 1860.

(4.) On Post-Tertiary Fossils from Labrador.-Ib. 1860. (5.) On the Geology of Murray Bay (Part 3, Post-pliocene deposits)-Ib. 1861.

(6.) Address as President of the Natural History Society of Montreal.-Ib. 1864.

(7.) On the Post-pliocene Deposits of Riviere du Loup and Tadoussac.-Ib. 1865.

(8.) Comparison of the Icebergs of Belle-isle and the Glaciers of Mont Blanc, with reference to the Boulder-clay of Canada. Ib. 1866.

(9.) On the Evidence of Fossil plants as to the Post-pliocene climate of Canada.-Ib. 1806.

In addition to these papers I placed in the hands of Sir W. E. Logan, all my notes and lists of fossils up to 1863, for his Report. of that year; and gave a resumé of the subject, in so far as the Post-pliocene of the Acadian Provinces is concerned, in the second edition of my "Acadian Geology," published in 1868.

Much of the matter contained in these detached publications now requires revision, more especially the lists of fossils; and many additional facts have accumulated. I purpose therefore now to summarize the facts and conclusions of my previous papers and to unite them with the new facts, so as to present as complete a view as possible of the geology of the superficial deposits of Canada. I shall also prepare a complete list of the fossils up to date, with revised nomenclature and synonymy. In this last part of the work I have been aided by Dr. P. P. Carpenter and Mr. Whiteaves. I have had the benefit, in the case of several critical species, of the advice of Mr. J. G. Jeffreys, and Mr. R. MacAn

Quoted in this paper as the "Geology of Canada."

drew of London. I am also indebted to Mr. G. S. Brady for determining the Ostracoda, to the Rev. H. W. Crosskey for opportunities of comparing specimens with those of the Clyde Beds, and to Prof. T. R. Jones and Dr. Parker and Mr. G. M. Dawson for help with the Foraminifera.

The present memoir will, I am sure, be welcomed by all who are engaged in the study of the subject to which it relates, if for no other reason, because the Post-pliocene deposits of Canada from their great extent and perfect development, are well fitted to throw light on many of the controversies which are now agitated with regard to these deposits.

It may be proper here to indicate the nomenclature which will be followed. When the whole geological series is divided into Primary, Secondary, and Tertiary, the deposits to which this paper relates are usually named Post-tertiary or Quaternary. These terms are, in my judgment, unfortunate and misleading. If we take the relations of fossils as our guide, then, as Pictet has well remarked, whether we regard the land or the sea animals, there is no decided break between the Newer Pliocene and the Post-pliocene, the changes not being greater than those between the Pliocene and the older Tertiary ages. There is, therefore, no such thing in nature as a Quaternary time distinct from the Tertiary, as the Tertiary is distinct from the Secondary. Where therefore the terms Primary, Secondary, and Tertiary are used, the latter should include the whole time from the Eocene to the modern, inclusive, unless indeed the advent of man be considered an event of sufficient geological importance to warrant a separation of the modern from the Tertiary period. When the terms Palæozoic, Mesozoic and Kainozoic or Neozoic are used, then the two latter terms cover perfectly the Post-pliocene as well as the Eocene, Miocene and Pliocene.

I would therefore include the Post-pliocene in the Neozoic or Tertiary period and define it to be that geological age which is included between the Pliocene and the Recent. From the former it is separated by the advent of the cold or glacial period, and the accompanying subsidence of the land, as well as by the disappearance of many species of animals and plants. From the latter it is separated by the extinction of many mammalian

I use the term "glacial" in this paper in its general sense, as including the action of floating ice as well as of land ice.

forms and by the establishment of our continents at their present elevation above the water and with their present fauna and flora and drainage systems. In Canada the absence of the Pliocene deposits and the immediate superposition of the Post-pliocene on the Palaeozoic formations, remove all difficulty on the subject. of the beginning of the period. The line of separation between the Post-pliocence and the recent, especially in Western Canada, is less distinct; but in Eastern Canada the upper part of the Postpliocene is always marine, while the recent deposits are land and fresh-water.

With regard to the subdivisions of the Post-pliocene in Canada, if we confine our attention to the clearly marked marine and glacial beds of the lower part of the St. Lawrence Valley, we have no difficulty in establishing the following divisions, suggested in my paper of 1857:

2.

Suxicava Sand, shallow-water sand and gravels, equivalent
to the Champlain and Terrace epochs in part of Dana, to
the modified drift of Hitchcock in part, to the Tertiary
sands of Capt. Bayfield; and to the Upper fossiliferous
sands and gravels of Scotland and Scandinavia.
Leda Clay, moderately deep-water clays, equivalent to lower
part of Champlain epoch, Dana, and Tertiary clays of
Bayfield. Fossiliferous Clays of Scotland and Scandi-
navia.

3. Boulder-Clay.-Hard clay or sometimes sandy clay or sand, with stones and boulders, and not distinctly laminated. Equivalent to Glacial clays of Dana and unmodified drift of Hitchcock. Till and older Boulder-clay of Scotland and Scandinavia.

In Lower Canada these three deposits can often be seen in actual superposition, and the order is invariable. In some places all contain marine shells, in others these are limited to the upper part of the Leda clay or the lower part of the Saxicava sand.

In Western Canada, around the great lakes, are extensively distributed beds of clay and gravel, which have been described in the Report of the Geological Survey, and which have afforded freshwater and land remains only. Of these the Algoma sand and Saugeen clay and sand may possibly correspond in age to the Saxicava sand, and the Erie clay to the Leda clay. This identification is, however, uncertain, as the marine Leda clay has been traced up no further than the vicinity of Kingston, on the St.

Lawrence, and of Arnprior on the Ottawa. Below these points the Valleys of the Ottawa and St. Lawrence present everywhere. the deposits above tabulated, in a greater or less degree of completeness. They are connected with the similar deposits of New England, through the valley of Lake Champlain, and across the low lands of Nova Scotia and New Brunswick.

Whittlesey has described the Western Drift Deposits in the Smithsonian Contributions, vol. xv., and according to him the Boulder drift is there the upper member of the series. More recently Prof. Newberry has given a summary of the facts in his Report of the Geological Survey of Ohio for 1869. From these sources I condense the following statements,

The lowest member of the Western drift, corresponding to the Erie clays of the Canadian Report, is very widely distributed and fills up the old hollows of the country, in some cases being two hundred feet or more in thickness. Toward the north these clays contain boulders and stones, but do not constitute a true Boulder-clay. They rest, however, on the glaciated rock surfaces. They have afforded no fossils except drifted vegetable remains.

Above these clays are sands of variable thickness. They contain beds of gravel, and near the surface teeth of elephants have been found. On the surface are scattered boulders and blocks of northern origin, often of great size, and in some cases transported two hundred miles from their original places.

More recent than all these deposits are the "Lake Ridges" marking a former extension of the great lakes. Dr. Newberry considers the Erie clay to be the deposit of a period of submergence following the action of a continental glacier, and he maintains that the old channels now filled with Erie clay are so deep as to indicate that in the earlier glacier period the land was at least five hundred feet higher than its present level. At the close of this period of submergence the boulder drift was deposited by northern currents and ice, and then the land gradually rose to its present level.

The facts thus summed up by Dr. Newberry indicate, in proceeding from the older to the newer.

1. An elevated continent and the erosion of deep valleys. 2. Glaciation of the surface.

3. Filling of the valleys with Erie clay.

4. Distribution over the surface, of boulders and Northern drift.

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