CHAPTER IX.

ORGANIC REMAINS IN MARINE DEPOSITS.— MODIFICATION OF CONDITIONS ON COASTS OF AMERICA.-OF PACIFIC OCEAN.-OF THE INDIAN OCEAN.-OF COASTS OF AFRICA AND EUROPE.-OF ARCTIC SEA.-DISTRIBUTION OF MARINE LIFE.-MODIFICATIONS FROM TEMPERATURE AND PRESSURE. FROM LIGHT AND SUPPLY OF AIR.-RESEARCHES OF PROF. E. FORBES IN THE ÆGEAN SEA.-ZONES OF DEPTH.-PROF. LÖVEN ON THE MOLLUSCS OF NORWAY.-ZONES OF DEPTH IN THE BRITISH SEAS.-ORGANIC REMAINS DEPOSITED IN THE DEEP OCEAN.-ON COASTS.

It is in connexion with the sea, looking at the evidence afforded us by the various fossiliferous rocks of different geological ages, that we should look for the preservation of the great mass of animal remains amid the detrital and chemical deposits of the time. We have seen that, by means of rivers and winds, various plants and animals, or their parts, may be borne into the sea, and that in estuaries we may have a mixture of terrestrial and marine remains, and of others suited especially to such situations. In respect to estuaries, some so gradually change into arms of the sea, to be seen on the large scale in the Gulf and River of St. Lawrence, and other situations, and equally well in numerous localities of far less area, in various parts of the world, as for instance, in the Bristol Channel and the Severn estuary, that no marked distinctions can be drawn between the one and the other.

Viewing the coasts of the world generally, we not only have to regard all the modifications for the existence of marine animal life, arising from the more or less exposed or sheltered situations of headlands, bays, and other forms of shore, but also the mingling of fresh waters with the sea under the various circumstances connected with the drainage of the land into the sea. Let us consider the modifications of condition for the existence and entombment of marine animal life from Cape Horn to Baffin's Bay. First, there is the difference of climate, producing modifications of no slight order, more especially in moderate depths. From Cape Horn to the

West India Islands, with the exception of the Straits of Magellan, there is an unbroken oceanic coast, subject to the action of the tides, upon which bodies of fresh water are thrown by drainage channels in different places, the chief of which are the Rio de la Plata, the Rio de San Francisco, the Tocantins, the Amazons, and the Orinoco rivers, delivering the portion of rains and melted snows not taken up by the animal and vegetable life, or required for the adjustment of springs or other interior conditions of a large part of South America. After a line of coast little broken by rivers, we find extensive estuary conditions at the mouth of the Plata, and not far beyond Lake Mirim, about 100 miles long, a body of water apparently cut off from the ocean by coast action, and draining into another lake or lagoon, Lago de los Patos, having a channel still open to the main sea, and about 150 miles long, with an extreme breadth of about 50 miles. In these two bodies of water, receiving the drainage of the adjoining land, there are necessarily modifications of the ocean conditions for life, and for the entomb

ment of its remains outside in the main sea. A range of coast succeeds, to which comparatively small rivers discharge themselves, until the San Francisco presents itself, and so on afterwards until the mouths of the Para and Amazons join in forming (including between them the Island of Marajo) great estuary conditions, the tides being felt up the latter river, it is stated, 600 miles, so that there are several in the river at the same time.

The mouths of the Orinoco present us with delta-form accumulations, and then comes the Carribbean Sea influenced by the ponded-back waters of the Gulf of Mexico, so that a kind of tideless sea shades into one where the tides are more felt. More northerly the Gulf stream is seen, transporting warmer waters to colder regions, and skirted by a shore, marked by a line of lagoons for above 200 miles on the coast of Florida, one of them named the Indian river, about 110 miles in length, with an extreme breadth of 6 miles; another, the Mosquito lagoon, being about 60 miles long, with the like extreme breadth. Thence a much-indented shore, on the minor scale, continues until we come to Cape Fear (Carolina), where the lagoon conditions obtain, a kind of barrier, broken by passages termed inlets, permitting the ingress and egress of sea waters. In Core, Pamlico, Albemarle, and Currituck Sounds, we find a great body of water of an irregular shape, measuring along the line of barrier separating them, except where broken by inlets from the ocean, about 160 miles in length. Rivers drain into this body of water in various directions, so that estuary conditions obtain

in different places, while the great barrier banks, a point of one of which forms Cape Hatteras, place it under a modification of the conditions outside in the main sea. More northward, we obtain the great indentation of Chesapeak Bay, with its minor breaks into the land, the chief of which is the Potomac; and then the Delaware Bay, with its river extending inland, the lagoon coast and its inlets continuing from Cape Charles (north entrance of Chesapeak Bay) towards the Delaware, and from near Cape Mary (Delaware Bay), about 85 miles to the northward. Next follows the mouth of the Hudson, and the modifications arising from the shelter of Long Island up the sound at its back, the lagoon character still apparent on part of its ocean coast. After shores variously indented, we reach the Bay of Fundy with all the modifications due to the great rise of tide (p. 78) at its northern extremities. This is succeeded by the great estuary conditions of the St. Lawrence, and finally the large indentions of Baffin's Bay and Strait and Hudson's Bay and Strait, and all the other channels of the cold regions of North America communicating with the Atlantic Ocean.

It is impossible, when directing our attention to this long line of coast, so variously modified in character, and necessarily so different in climate, not to see how very modified must also be the conditions for the existence of life and the preservation of any of its harder parts. One contemporaneous coating of sedimentary or chemically deposited matter must include the remains of very different creatures, either living upon or in the surface accumulations, as well as the vegetable and animal remains drifted into it from the land. The molluscs inhabiting the coasts of the cold regions would be expected to differ materially from those in the tropics, and the plants and terrestrial animals and amphibious creatures of the latter would vary from those in the former. The organic remains buried in the deposits of the Gulf of Mexico, though entombed at the same time as those in Baffin's Bay, could scarcely be expected to offer the same cha

racters.

If, instead of the eastern coast of America, we look to the western, the first marked difference which presents itself is the absence of great rivers up the whole of the southern Continent and the land connecting it with the wide-spread northern part. Numerous sheltered situations are to be found amid the islands and inlets extending from Cape Horn to, and including the island of, Chiloe; after which, for about 6000 miles of coast, to the Gulf of California, the shores are little broken by indentations, except at Guayaquil and Panama, and do not present a single estuary of importance as on the eastern

side of the continent. The mixture of fresh water with the oceans on either side is very different, as are also the conditions for estuary life and the transport of terrestrial and fluviatile organic remains for entombment in the coast sedimentary accumulations. Even after we have passed the Gulf of California, and the Colorado delivering its waters at its head, there is, for about 2000 miles, from Cape S. Lucas to Vancouver's Island, a slightly-indented coast and a minor discharge of drainage waters, with the exception of those delivered by the Columbia or Oregon. Subsequently more northward, for about 800 miles, islands and inlets are common, offering modifications for the existence of marine life, as regards shelter and exposure to waves produced by winds, to Sitka Island and Cross Sound. After which comes the variously-indented coast extending to the Aleutian Islands, and so on to Behring Straits.

Though we have the same range through climates, the character of the two coasts of the American continent varies so materially that we can scarcely but expect very important modifications, as well in the life as in the physical conditions under which it is placed. We have not only to regard the very great difference in the amount of fresh waters discharged on the east and on the west, with its consequences, but also the ponded waters of the Mexican Gulf and their continuation into the Carribbean Sea, with the result, the Gulf Stream, on the one side and not on the other, not neglecting the important difference presented by the great Mediterranean Sea, of Hudson's Bay and Baffin's Bay on the east, and the kind of coast found on the west. To this also should be added the great barrier offered by America to the passage of tropical marine animals from one ocean to the other.*

It may be useful to glance at the great modification of conditions on the western side of the Pacific. Though a great portion of the drainage of Asia is disposed of in other directions, the surplus waters of a large area still find their way to the east coast. The

According to M. Alcide d'Orbigny, of 362 species of molluscs in the Atlantic and Great Oceans, there is only one common to both, Siphonaria Lessoni. Of these 362 species, omitting the last, 156 belong to the Atlantic, and 205 to the Great Ocean. He also remarks that, if the two sides of the American continent be compared, the proportion, in the Atlantic, of gasteropod to lamellibranchiate molluscs, is 85 to 71, while in the Pacific it is 129 to 76. Of 95 genera considered to be proper to the shores of South America, 45 only are common to the two seas. This M. D'Orbigny attributes to the steep slopes of the west side, the Cordilleras rising near the coast, and rocks being more numerous than sandy shores, so that gasteropods would be expected to be more common, while the Atlantic coasts present mud, silt, and sand in great abundance, with gently-sloping shores for a large proportion of their length.— Récherches sur les lois qui Président à la Distribution des Mollusques Côtiers Marins. Comptes Rendues, vol. xix. (Nov. 1844). Ann. des Sciences Naturelles, Third Series, vol. iii., p. 193 (1845).

Saghalian river throws its waters, derived from a considerable area, behind the island of the same name, to be driven into the Okhotsk Sea on the north, or the Japan Sea on the south, as the case may be. Both these seas are, to a certain extent, separated from the main ocean by the range of islands, composed of the Kourile and Japanese islands, extending from Kamschatka to Corea, the Japan Sea especially, from the great mass of island land interposing between it and the Pacific, offering the character of a Mediterranean Sea. Proceeding southerly we arrive at the Yellow Sea, which receives the abundant drainage effected by the Hoang Ho and its tributaries, and more southerly still we find the body of fresh water discharged into the sea by the Yang-tse-kiang. Thence, to the south, until the Si-kiang with its tributaries presents itself in the Canton estuary, comparatively minor rivers flow into the ocean, the coast being much indented, smaller rivers and streams often discharging in the upper parts of the indentations.

The Island of Hainan, with the great promontory stretching to meet it from the main Chinese land, forms the Gulf of Tonquin, into which the San-koi and other rivers discharge their waters. The amount of fresh water poured into the sea on the eastern coast of Cochin China is subsequently of no great importance, and it is not until we arrive at the delta of the Maikiang or Camboja that the sea is much influenced by the influx of fresh waters, an influence again, however, to be repeated at the head of the Gulf of Siam, by the outpouring of the Meinam, a river remarkably parallel with the Maikiang for about 700 miles, the latter holding a singularly straight course, as a whole, to the N.N.E., for about 1750 miles. The remaining portion of the Asiatic continent, formed by the Malayan promontory, throws no important body of fresh waters into the sea in the form of a main river.

From Kamschatka nearly to the equator we thus have a continental barrier, for the most part not wanting in the outflow of bodies of fresh water, sufficient to produce marked influences on parts of the coasts, and consequently upon the conditions under which animal life may exist along it, and the remains of terrestrial and fluviatile plants and animals be drifted outwards into any sedimentary or chemical deposits now forming adjoining it. Minor parts of the ocean are also, to a certain extent, separated off by islands, the range of the Philippines and Borneo, in addition to those mentioned, tending to portion off the ocean down to the

Considering the inference to be correct, as it appears to be, that the Latchou is the upper part of the Maikiang.