Edward Forbes

“ The distribution of our native marine fishes exhibits distinctly four types, of which two, a northern and a southern, belong to great ichthyological provinces, the bounds of which approach, but can scarcely be said to meet in our seas—and two, a British and an oceanic, the former including those species either peculiar to or chiefly developed in the British Seas, and of which the Irish Sea may be regarded as the centre or capital, and the latter of pelagic forms occasionally or frequently visiting our shores in common with most of the coasti of the north Atlantic. ”

“ In one point our parallel fails us. The great pachyderms which appear to have inhabited Britain after the Drift period, and the assemblage of horses and hyenas have no analogues in the zoological provinces of Boreal America. Every where in the northern hemisphere these remarkable animals appear to have lived during the epoch preceding the historical, and to have become extinct before the advent of man. ”

“ The phenomena of the glacial formations, the peculiarities in the distribution of the animals of that epoch, and in the relations of the existing fauna and flora of Greenland, Iceland, and northern Europe are such as strongly to impress upon my mind, that the close of the Glacial epoch was marked by the gradual submergence of some great northern land, along die coasts of which the littoral mollusks, aided by favouring currents, migrated, whilst a common flora became diffused over its hills and plains. ”

“ The assemblage of plants (small as to number of species but playing an important part in the general vegetation) giving a peculiar and very remarkable character to the flora of a considerable part of the west of Ireland.
These three sub-floras are all allied to, and derived assemblages of European plants south of the great Germanic group. As the south of England and of Ireland were in all probability unsubmerged during the Glacial epoch, they may have come over either before, or during, or after that period. There are strong reasons for believing they migrated before. ”

“ The coral-like Nullipora is the last and bounding plant of this zone in our seas, and rarely ranges with us below 20 fathoms at the utmost; though in more southern seas, as in the Mediterranean, it is found abundantly at depths as great as 70 and 80 fathoms, where, as here, it forms the out-post of marine vegetation in depth. [14] The third province in depth I have termed the Region of Corallines, for in it we find the greatest variety and abundance of the corneous zoophytes—arborescent animals, which seem here to take the place of plants. ”

“ There remains the third mode by which a land may be peopled; namely, by colonization from another or from several neighbouring lands previous to isolation. This, of course, involves the consideration of geological causes, the part played by which in the present disposition of organized beings on the surface of our globe, has never as yet received due consideration. It is through this mode, I believe, the British Islands have chiefly acquired their fauna and flora ”

“ The alpine floras of Europe and Asia, so far as they are identical with the flora of the Arctic and sub-Arctic zones of the Old World, are fragments of a flora which was diffused from the north, either by means of transport not now in action on the temperate coasts of Europe, or over continuous land which no longer exists. The deep-sea fauna is in like manner a fragment of the general glacial fauna. ”

“ No glacial beds are known in southern Europe; no "newer pliocene" (in the sense of equivalents of the Sicilian tertiaries) , in the centre and north. In the latter we find most of the existing British testacea, which after inhabiting our area before, disappeared from it during the Glacial epoch; and with them we find certain glacial species of northern origin, now extinct in the seas of southern Europe. I infer the synchronism of the glacial and Sicilian deposits. ”

“ In summing up his results, he notices the collision of the two types of marine fauna alluded to as follows: "Cape Cod, the right arm of the commonwealth, reaches out into the ocean some fifty or sixty miles. It is nowhere many miles wide; but this narrow point of land has hitherto proved the barrier to the migrations of many species of Mollusca. Several genera and numerous species, which are separated by the intervention of only a few miles of land are effectually prevented from intermingling by the cape, and do not pass from one side to the other. ”

“ The marine shell-constructing Annelida present some peculiarities of distribution worthy of notice by geologists, such as the prevalence of Serpula serrulata in the deeper regions of the northern provinces and the constant occurrence of species of Ditrupa at great depths in several parts of our seas far from land.
Our knowledge of the species and distribution of the British Mollusca is very complete, and sufficient to enable us to apply it to the elucidation of geological problems with safety and effect. ”

“ The northern and western relations of the glacial testacea are very remarkable. Not only are several of the characteristic species, as we have already seen, identical with forms now known only in Arctic Seas, or on the coasts of Boreal America, but fully a third of the entire assemblage are species still existing in the American Seas, and at the same time on the coasts of Europe. ”

“ In the preceding summary view of the regions or provinces into which our flora and fauna may be divided, I have gone into no further detail than is necessary for the display of their principal and characteristic features, such as may be grasped by persons not familiar with the abundant details and materiai amassed in our British faunas and floras, which are more complete probably than those of any other country. ”

“ In all questions respecting the age of sedimentary strata, the evidence afforded by the fossilized remains of mollusks must, from its completeness, always take precedence of that derived from any other class of animals. Though our native existing species have been well determined, there is no one work upon them to which the geologist can be referred with safety, nor any comprehensive essay as yet published on their distribution. ”

“ Whilst it is very probable that in the present state of the inquiry—its infancy, in fact—there are many of my data insecure and likely to require considerable modification hereaiter, the great leading principle, I firmly believe, will stand the strictest investigation, and prove as true when tested by an appeal to the distribution of organized beings, as well fossil as recent, over the whole globe—as well during the several geological epochs of ancient times as in that in which we live, as it appears to be when applied to the limited area under consideration. ”

“ The specific identity, to any extent, of the flora and fauna of one area with those of another, depends on both areas forming, or having formed, part of the same specific centre, or on their having derived their animal and vegetable population by transmission, through migration, over continuous or closely contiguous land, aided, in the case of alpine floras, by transportation on floating masses of ice. ”

“ In the case of the alpine flora of Britain, the evidence of the activity of the law and the influence of the accident are inseparable, the law being maintained by a transported flora, for the transmission of which, I have shown, we can account by an appeal to unquestionable geological events. ”

“ The British formations of the glacial epoch present themselves in the form of partially stratified, or often entirely unstratified beds of clay, marl, sand, and gravel, varying greatly in different localities; in many places charged with rounded boulders. Generally the clays and marls are inferior to the gravels and sands. They are to be met with in many parts of both east and west of Scotland; on both sides of the north of England; in Wales; through a great part of Ireland, and in the Isle of Man. ”

“ It is well known, that this correspondence is recognised in the general facies of the flora and fauna, dependent on generic correspondences, specific representations, and, in some cases, specific identities. But when announcing and illustrating the law that climatal zones of animal and vegetable life are mutually repeated or represented by elevation and latitude, naturalists have not hitherto sufficiently (if at all) distinguished between the evidence of that law, as exhibited by representative species and by identical. ”

“ The deepest of the submarine localities, which may be considered as Arctic outhers, with the fauna of which I am acquainted, is one in Loch Fyne, examined by Mr. MacAndrew and myself on the 16th of August, 1845. The dredge brought up eight species of testaceous mollusca, one crustacean, and two echinoderms. So small a number of species among the contents of a full dredge is remarkable and rare, and itself a fact indicative of great depth. Of these mollusca five species were alive. ”

“ For, when we consider that within this limited area a great number of animals and plants are not universally dispersed, but congregated in such a way as to form distinct regions or provinces, which have remained unchanged as long as we have any record, we can hardly grant transporting powers to have operated so far as to sketch out those regions in the likenesses of distant and distinct lands, and yet not afterwards to have continued their action, so as eventually to have merged them all into an homogeneous whole. ”

“ Every plant universally distributed in these islands is Germanic; every quadruped common in England, and not ranging to Ireland or Scotland. The great mass of our pulmoniferous mollusca have also come from the same quarter. Certain botanical and zoological peculiarities are presented by the eastern counties of England. In every case we find these to depend on Germanic plants and animals arrested in their range. The number of species of the Germanic type diminishes as we go westwards, and increases when we cross the German Ocean. ”

“ The zoological works of Fleming, Jenyns, Yarrell, Bell, and W. Thompson, have enumerated the species and treated of the distribution of our indigenous animals, those of Smith, Hooker, Lindley, Babington, Henslow, and especially Watson, have done the same service for our native flora; but the history of the formation, if I may so say, of that fauna and flora, remains to be investigated. This essay is offered as a contribution towards such a history.
There are three modes in which an isolated area may become peopled by animals and plants. ”

“ I have compared it with the Mitra groenlandica (specimens of which are in the British Museum) of Möller, a species which we may expect possibly to be preserved in the drift. The Greenland shell is about the same size as our fossil, but in other respects is very different. The existence of a Mitra in Greenland is an apparent anomaly in the distribution of the species of that genus, which would seriously militate against the idea entertained by many naturalists (and to which I am inclined to subscribe) of the existence of generic centres. ”

“ The increase, too, of northern forms, is very marked, 41 out of the 60 being species which occur fossil in the "northern drift." Of these, 19 are common to the coasts of Britain and America, and are associated with four species now known living only in the Arctic or Boreal-American Seas. The American Cancellaria also lived in our area during this epoch. All the British species found in the red crag, which are not known in the preceding formation, are of northern origin. The rest of the red crag molluscan fauna is made up of species either southern or extinct. ”

“ Such a deficiency in species and individuals of the testaceous forms of mollusca, indicates, to the marine-zoologist, the probability of a state of climate colder than that prevailing in the same area at present. Thus the existing fauna of the Arctic Seas includes a much smaller number of testaceous mollusks than those of mid-European Seas, and the number of testacea in the latter is much less than in south-European and Mediterranean regions. ”

“ Loc., fossil. Sweden.
Loc., living. In local patches (Boreal) in the British Seas, chiefly on the coast of Scotland, where it grows to a great size, and is very abundant in particular localities, as Loch Fine. Its usual range is from 15 to 30 fathoms, and it has been taken by Mr. MacAndrew and myself as deep as 80 fathoms, more than 20 miles from the nearest land. It occurs in more northern latitudes on the Scandinavian coast; also in the seas of Boreal America. South of Britain it is apparently confined to very deep water, and has been taken in the Mediterranean. ”

“ I have used it, however, for want of a better, and as an expression of convenience, always intending to express by the phrase "Glacial epoch" that section of geological time which was typically distinguished by the
prevalence of severe climatal conditions through a great part of the northern hemisphere, and during which those marine accumulations, in part truly sedimentary deposits, which have been called "Northern drift," were formed. ”

“ The abundance of animal life in the littoral zone and its respective sub-divisions must not be judged of from the number of species named in this table—my object at present being not to give lists of their flora and fauna, but to show how well marked, by characteristic forms, such zones are. ”