# Memoirs of the Geological Survey of Great Britain/Volume 1/On the Connexion between the Distribution of the existing Fauna and Flora of the British Isles

In the following remarks on the history of the indigenous fauna and flora of the British Islands and the neighbouring sea, I take for granted the existence of specific centres, i.e., of certain geographical points from which the individuals of each species have been diffused. This, indeed, must be taken for granted, if the idea of a species (as most naturalists hold) involves the idea of the relationship of all the individuals composing it, and their consequent descent from a single progenitor, or from two, according as the sexes might be united or distinct.
That this view is true, the following facts go far to prove. 1st. Species of opposite hemispheres placed under similar conditions are representative and not identical 2nd. Species occupying similar conditions in geological formations far apart, and which conditions are not met with in the intermediate formations, are representative and not identical. 3rd. Wherever a given assemblage of conditions, to which, and to which only, certain species are adapted, are continuous—whether geographically or geologically—identical species range throughout.
I offer no comments on these three great facts, which I present for the consideration of the few naturalists who doubt the doctrine of specific centres. The general and traditional belief of mankind has connected the idea of descent with that of distinct kinds, or species, of creatures; and the abandonment of this doctrine would place in a very dubious position all evidence the palæontologist could offer to the geologist towards the comparison and identification of strata, and the determination of the epoch of their formation.
Moreover, it is notorious that the doctrine of more than one point of origin for a single species, and consequently more than one primogenitor for the individuals of it, sprung out of apparent anomalies and difficulties in distribution, such as those which I am about to show can be reasonably accounted for, without having recourse to such a supposition.
Having assumed the doctrine of specific centres as true, the problem to be solved is, the origin of the assemblages of the animals and plants ​now inhabiting the British Islands. 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.
1st. By special creation within that area.
2nd. By transport to it
3rd. By migration before isolation.
The first of these modes, if it operated at all within the limited area under examination, had but very little influence in determining the vegetation and animal population of the British Isles, since, with a very few, mostiy doubtful, exceptions, the terrestrial animals and flowering plants within their area are identical with continental species.
The second mode is not a sufficient one; for, though doubtiess the great mass of cryptogamic plants, a few phanerogamia, and a few terrestrial animals, besides those endowed with powers of flight, may have found their way across the separating waters by the agency of currents, &c., or in the case of plants, their seeds have been conveyed by the winds or birds through the air, yet, after making full allowances for all likely means of transport at present in action, there remains a residue of animals and plants which we cannot suppose to have been transported, since either their bodily characters or certain phenomena presented by their present distribution, prevent our entertaining such an idea. 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.
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; but, before showing how, it may be well to point out certain peculiarities presented by their ​natural history, well known and placed on record by British botanists and zoologists. The consideration of them has caused me to make this attempt towards ascertaining the causes by which they were produced.
The vegetation of the British Isles presents a union of five well-marked floras, four of which are restricted to definite provinces, whilst the fifth, besides exclusively claiming a great part of the area, overspreads and commingles with all the others.
I. Commencing with the smallest, we find the mountainous districts of the west and south-west of Ireland characterized by botanical peculiarities which depend on the presence of a few prolific species belonging to the families Saxifrageæ, Ericaceæ, Lentibulariæ and Cruciferæ. The nearest points of Europe where these plants are native is the north of Spain. The species are—
Saxifraga umbrosa. Saxifraga elegans. Saxifraga hirsuta. Saxifraga Geum. Saxifraga hirta. Saxifraga affinis. Erica Mackaiana. Erica mediterranea. Dabæcia polifolia. Arbutus unedo. Pinguicula grandiflora. Arabia ciliata.
There are two or three other species, including Allium Babingtonii, whichpossibly belong to the same assemblage.
There is no evidence of any local assemblage of animals corresponding to this flora.
II. In the south-west of England and south-east of Ireland we find a flora which includes a number of species not elsewhere seen in the British Isles, and which is intimately related to that of the Channel Isles, and the neighbouring part of France. In the Channel Isles we find them associated with a number of plants which are not natives of England or Ireland. Such are Ranunculus ophioglossifolis, Sinapis cheiranthus, Erucastrum incanum, Arthrolobium ebracteatum, Centaurea Isnardi, Linaria pelisseriana, Echium violaceum, Orchis Laxiflora, Allium sphærocephalum, &c., plants which mark the commencement of the type of vegetation characteristic of Southern Europe. They are accompanied by terrestrial mollusca of the same climatal stamp, such as Helix aperta and Helix revelata, both first noticed in Guernsey by myself in 1839; the former is there at its most northern limit, and the latter only extends further into Devonshire. Thither it accompanies a ​number of plants of the same climatal type with those enumerated above, but whose range does not extend beyond this corner of England. Such are Helianthemum polifolium, Tamarix gallica, Hypericum linearifolium, Oxalis corniculata, Lotus hispidus, Corrigiola littaralis, Polycarpon tetraphyllum, Bupleurum aristatum, Physospermum cornubiense, Lobelia urens, Erica ciliaris, Salvia clandestina, Trichanema columnæ, and Scilla autumnalis.
In the south-east of Ireland we find the number of plants of this Gallican type greatly diminished; whilst such as are present are species met with also in the south-west of England. Such are Matthiola sinuata, Senebiera didyma, Medecago denticulata, Rubia peregrina, Antirrhinum orontium, Linaria elatins and italica, Scrophularia scorodonia, Sibthorpia Europæa, Erica vagans, Cicendia filiformis, Teucrium scordium, Hottonia palustris, and others.
This is the Atlantic type in Mr. Watson's arrangement of British types of vegetation.
Helix pisana extends its range through a great part of this region. Testacellus haliotoideus is confined to the English portion of it. This was possibly the parent British fauna of Bulimus acutus. The presence of the Bufo calamita (the Natter Jack) in Ireland is probably also proper to this province.
III. In the south-east of England, where the rocks of the cretaceous system are chiefly developed, we find the vegetation distinguished by the presence of a number of species common to this district and the opposite coast of France. Here are the localities of the well-known chalk plants, much sought after by botanists from the north. They form part of Mr. Watson's second, or Germanic, and of his third, or English, type of British vegetation.
Thlaspi perfoliatum, Linum perenne, Genista pilosa, Onobrychis sativa, Bryonia dioica, Caucalis daucoides, Dipsacus pilosus, Inula conyza, Centaurea calcitrapa, Phyteuma orbiculare, Gentiana pneumonanthe, Verbascum lychnitis, thapsiforme, and blattaria, Salvia pratense, Ajuga chamæpitys, Buxus sempervirens, Tamus communis, and many species of Orchideæ, though not all chalk plants, are members of this flora. Clematis vitalba, and some other plants, appear to be equally members of it, and of the last region.
The peculiar character of the entomology of the south-east of England is intimately connected with the presence of this flora, and also that of the pulmoniferous mollusca, which here include several species, as Helix pomatia, Helix obvoluta, Helix limbata, Helix carthusiana and carthusianella, Clausilia ventricosa, Clausilia Rolphii, and Bulimus montanus, either confined to this district, or very rarely found beyond it in Britain.
​IV. The summits of our British Alps have always yielded to the botanist a rich harvest of plants which he could not meet with elsewhere among these islands. The species of these mountain plants are most numerous on the Scotch mountains,—comparatively few on more southern ridges, such as those of Cumberland and Wales. But the species found on the latter are all, with a single exception (Lloydia serotina), inhabitants also of the highlands of Scotland; whilst the alpine plants of the Scotch mountains are all in like manner identical with the plants of more northern ranges, as the Scandinavian Alps, where, however, there are species associated with them which have not appeared in our country. This progressive diminution of alpine forms southwards is an important fact, the interpretation of which will presently appear.
The first plant of this Scandinavian type which disappears southwards is the Arenaria norvegica, confined to the most northern of the Shetland Isles. On the northern shores of the mainland a beautiful primrose, the Primula scotica, formerly supposed to be peculiar to the country after which it is named, but found by me abundantly in Norway in 1833, appears and ceases. A rich assemblage of these northern forms are distributed over the Scottish Alps, but do not reach the English mountains. Such are Draba rupestris, Lychnis alpina, Arenaria rubella, Astragulus alpinus, Sibbaldia procumbens, Saxifraga cernua, Saxifraga rivularis, Arctostaphylos alpina, Phyllodoce cœrulea, Azalea procumbens, Gentiana nivalis, Myosotis suaveolens, Veronica alpina, Veronica saxatilis, Salix arenaria, Betula nana, and many species of Juncus, Luzula, and Carex, Of these the Phyllodoce cœrulea (a plant highly characteristic of the Norwegian Alps) has either disappeared lately, or is likely soon to be extirpated, having fallen a victim to the ardour of collectors, who will, probably, ere long, extirpate many more of our alpine rarities, and reduce them to the rank of doubtful natives—like Eriophorum alpinum, now certainly extinct. To the same category with the above belong some plants less truly alpine, and not ranging south of Scotland, as Moneses grandiflora, Pinguicula alpina, Ajuga pyramidalis, Goodyeria repens, 'Corallorhiza innata, and certain species which reach the north of England, as Cornus suecica, Linnæa borealis, and Trientalis Europæa, all very characteristic Scandinavian species. To the Welsh mountains but few of these alpine and northern forms reach, but among them are some of the most characteristic. Such are Arabis petræa, Cerastium alpinum, Potentilla alpestris, Sedum villosum, Saxifraga muscoides, Saxifraga nivalis, Erigeron alpinum, Salix reticulata and herbacea, Juncus filiformis, and Juncus triglumis.
In Ireland, also, a few of these alpine or sub-alpine plants of Scandinavian origin are found, probably derived from the same source, and ​with them some of those inhabiting the low country, such as Lamium intermedium, a common plant also in Scotland.
The fauna of our mountain regions, so far as it is developed, bears the same relation to more northern countries. The alpine hare (Lepus variabilis), the ptarmigan, and the capercailzie (now extinct), may be cited among the higher animals; and the insects which give a character to the entomology of the Highlands are Scandinavian forms. The absence of peculiar pulmonifera is as good evidence as the presence of the insects, for whilst almost every mountain region in Europe is distinguished for its peculiar Helices and their allies, the British, like the Scandinavian Alps, are remarkable only for their deficiencies.
The Highland, and part of the Scottish and Hebridean types of British vegetation, as defined by Mr. Watson, agree with the fourth flora, as defined above. In his Hebridean type he includes the rare Eriocaulon septangulare, a very remarkable plant, known in Europe only in the Hebrides, and Connamara, in the West of Ireland; elsewhere it is an inhabitant of Boreal America, which is its true native country, and from whence, either by means of transport, now or anciently in action, it has, in all probability, been introduced naturally into the British Isles.
V. The fifth and general flora of the British Islands—everywhere present, alone or in company with the others—is identical as to species with the Flora of Central and Western Europe—that which may be properly styled Germanic. Such of its members as are generally distributed compose the British type of Mr. Watson, whilst its more local species are distributed among, and form part of his Germanic, English, and Scottish types. This is a flora which has overspread many local floras throughout Europe, and given a general character to the vegetation derived from the presence of such truly common species as Bellis perennis, Primula acaulis, Ranunculus acris, Ficaria ranunculoides, Cardamine hirsuta, and our most common trees and shrubs. Its scarcer plants are of more interest, from the clear manner in which they mark the progress of the flora, and the line it took in its advance westwards. Thus, we find still limited to the eastern counties of England, such species as Anemone pulsatilla, Myosurus minimus, Turritis glabra, Frankenia lævis, Holosteum umbellatum, Schleranthus perennis, Artemesia campestris, Melampyrum cristatum, Veronica verna, Veronica triphyllos, Stratiotes aloides, and Sturmia Loeselii. Others again, whilst they have extended over considerable tracts, or into several districts of England and Scotland, have not found their way to Ireland, as Thalictrum majus, Ranunculus hirsutus, Diplotaxis tenuifolia, Thlaspi alpestre, Lychnis viscosus, Stellaria nemorum, Genista anglica, Astragulus hypoglottis, Spiræa filipendula, Potentilla verna, Ligusticum scoticum, Valeriana dioica, Scabiosa columbaria, Campanula glomerata, Gagea lutea, Acorus ​calamus. Some, such as Primula farinosa, Lysimachia thyrsiflora, and Convallaria verticillata, seem to indicate a more northern point of derivation of this Germanic flora than that from whence the main part of its assemblage of plants came. It is remarkable that certain species of this flora, which flourish best on limestone, such as 'Scabiosa columbaria, Sison amomum, Campanula glomerata, and others, are not found in the limestone districts of Ireland, and in like manner certain species, which everywhere, when found, delight in sand, as Ajuga chamæpitys (more properly a member of III. than of V.), are also wanting on such Irish localities as are best adapted for them.
The fauna which accompanies this flora presents the same peculiarities, and diminishes towards the north and west. This is very observable, both among the native vertebrate and invertebrate animals. Thus, among quadrupeds, the mole, the squirrel, the dormouse, the polecat, and the hare of England (Lepus timidus), are confined to the English side of St. George's Channel, not to mention smaller quadrupeds. So it is also with the birds of short flight; so most remarkably, no less than half the species being deficient, with the reptiles; so also with the insects, and the pulmoniferous mollusca. Among the latter animals are several species, which mark the fauna of the Germanic type as distinct from those of the more southern provinces. Such are Helix scarburgensis and excavata, Clausilia dubia, and Pupa alpestris.
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. It is this very completeness which enables us to pursue such inquiries as the present, which, indeed, could not be entered upon with advantage unless there were abundant data gathered together. The essays of Mr. H. C. Watson may be cited as among the most remarkable, and to them I must refer geologists who would wish to learn more respecting our indigenous flora, than it is here necessary to state.
It cannot be expected that in this stage of the inquiry all exceptional cases in our flora and fauna can be explained. There are several extremely difficult of explanation, but they are neither so numerous nor of sufficient importance to afiect the general argument, and may safely be put aside for the present, in the certainty that the progress of research will ere long make clear the most doubtful.
To determine the how and when of these peculiarities, on the ​supposition that they are mainly due to—indeed, the only course left—migration before isolation of the area, it is necessary, if possible, to ascertain two fixed points in time, between which the migration or migrations must have taken place.
The eocene tertiary epoch—that of the deposition of the London clay—affords a first or most ancient point, after which only such migrations could have taken place; for we have abundant evidence that both the flora and fauna of such parts of the area under examination as were above water, were then very distinct from those which now occupy it, and enjoyed a climate far warmer than suitable to its present (terrestrial) inhabitants.
The epoch usually designated "historical"—that during which man has been a known inhabitant of the earth—affords a last point, one before which the migrations (at least, for the most part) took place. For the great deposits of peat, formed in part out of the remains of vast forests, which probably, during the earliest stages of the true historical epoch, covered a great part of the existing area of the British Isles, in many places overlie the fresh-water marls of the post-pliocene epoch, during which the Cervus megaceros flourished, themselves overlying and occupying depressions in the pleistocene tertiaries, formed of the upheaved bed of the sea of the glacial period.
During the post-pliocene epoch, over the elevated bed of the glacial sea, the great mass of the flora and fauna of the British Isles migrated from the Germanic regions of the continent The whole of the flora I have numbered V., including the great mass of British plants, is Germanic. 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. On the other hand, the peculiarities of the Irish and Scottish faunas and floras depend either on the presence of animals and plants which are not of the Germanic type, or on the absence of English species, which are. When we turn to plants and mollusks which affect localities presenting certain mineral peculiarities, such as limestone plants and animals, as they are called, and which are consequently never generally diffused, we find that the species of the Germanic type are deficient westwards—in Ireland, for instance, where conditions favourable to their presence and diffusion occur abundantly. To what else can we attribute such peculiarities, unless to arrestment of the ​migration of the Germanic types? And when we know that the Irish Sea is scooped out of the elevated bed of the sea of the glacial epoch, masses of which, of great extent and thickness, we find bounding its sides in England, the Isle of Man, and still more conspicuously in Ireland, and that on the great pleistocene plain lived the Cervus megaceros, can we doubt that over it the mass of Germanic types, forming the existing flora and fauna of Ireland migrated?—and that the migration of the species, less speedy of diffusion, which are now peculiar to England, was arrested by the breaking up of that land of passage—and thence the famous deficiencies of the Sister Isle, as for instance its freedom from reptiles, as, indeed, the excellent comparative Table of the Reptilia of Belgium, England, and Ireland, given by Mr. Thompson in his valuable Report on the Irish fauna, affords abundant proof.
| | Belgium. | Britain. | Ireland. |
| Sauria. | | | |
| Lacerta................................................................................................................................................................................................................................................................................................................................................................................................ | 3 | 2 | 1 |
| Anguis................................................................................................................................................................................................................................................................................................................................................................................................ | 1 | 1 | .. |
| Ophidia. | | | |
| Coluber................................................................................................................................................................................................................................................................................................................................................................................................ | 2 | .. | .. |
| Natrix................................................................................................................................................................................................................................................................................................................................................................................................ | 1 | 1 | .. |
| Vipera................................................................................................................................................................................................................................................................................................................................................................................................ | 2 | 1 | .. |
| Batrachia. | | | |
| Rana................................................................................................................................................................................................................................................................................................................................................................................................ | 2 | 1 | 1 |
| Bombinator................................................................................................................................................................................................................................................................................................................................................................................................ | 3 | .. | .. |
| Hyla................................................................................................................................................................................................................................................................................................................................................................................................ | 1 | .. | .. |
| Bufo................................................................................................................................................................................................................................................................................................................................................................................................ | 2 | 2 | 1 |
| Salamandra................................................................................................................................................................................................................................................................................................................................................................................................ | 1 | .. | .. |
| Triton................................................................................................................................................................................................................................................................................................................................................................................................ | 4 | 3 | 2 |
On what did the difference (which is wholly numerical, and not specific) between the reptile population of Britain and Belgium, exhibited in this table, depend? On the same cause on which the difference between the flora and fauna of the east of England and Germany depends—on the breaking up of the upheaved bed of the Germanic Ocean of the glacial period, which possibly, indeed probably, was effected more slowly, and completed at a later time than the separation of Britain and Ireland.
But though the migration of animals and plants over the great Germanic plain will account for the major part of our British species which come from the west, we have in the mountain districts of Scotland, England, and Wales, a considerable flora, and a portion of our fauna, which cannot be traced to such a source, seeing that they are ​not inhabitants of the ancient west of Europe, but of Scandinavia. How did they come? The alpine character of most of them forbids us by any stretch of probability to conduct them across the Germanic plain from its most northern bound, though some few plants, giving a peculiarity to the flora of the north-east of England and south-east of Scotland probably were so derived. But these I regard as Germanic. The plants and animals now under consideration could not have migrated hither after the destruction of the Germanic plains, for by that time the British Isles had assumed their present forms, and the localities of these species had become mountain tops. We have seen that the great Germanic and central British plains themselves were portions of the elevated bed of a pre-existing sea, which sea, when we trace its relics, is found to have covered a great part of the British Isles as now exposed, so that during its existence our mountains must have been comparatively low islands. This was the sea of the Glacial period, properly so styled, when the climate of the whole of northern and part of central Europe, was very different from what it is now, and far colder. The remains of the marine animals found in the strata deposited in that sea indubitably prove this fact, and, as will be seen presently, the flora of its islands as fully bears out such climatal evidence. This was the epoch of glaciers and icebergs, of boulders, and groovings, and scratches. It exhibited conditions physical and zoological, similar—indeed, nearly identical—to those now to be met with on the north-eastern coasts of America within the line of summer-floating ice. Extend that line across the southern half of Ireland and England,—not farther south, as we have evidence to show,—continue it eastwards, so as to strike against the Ural chain (as Sir Roderick Murchison has proved in his great work on Russia), and within that vast area you will have a condition of climate which will account for all the organic phenomena observed in the boulder clays and pleistocene drifts.
Now it was during this epoch (the epoch of my IVth flora), that Scotland and Wales, and part of Ireland, then groups of islands in this ice-bound sea, received their alpine flora and a small portion of their fauna. Plants of subarctic character then would flourish to the water's edge, but when a new state of things commenced, when the bed of the glacial sea was upheaved, its islands converted into mountains, its climate changed, and a suitable population of animals and vegetables diffused over its area, the plants of the colder epoch survived only on the mountain regions which had been so elevated as to retain climatal conditions similar to those which existed when those regions were low ridges or islands in the glacial sea.
The general fauna and flora of our country being accounted for, and ​also the peculiarities of the British alps, there still remain certain limited assemblages of organized beings which present distinctive characters, and for which the geological operations just referred to would not account. These are three in number. 1st. The animals and plants which give a peculiar character to the south-east of England, and inhabit, for the most part, the chalk districts. 2nd. The animals and plants which distinguish the south-west of England and the south- east of Ireland, species mostiy indigenous also in the Channel Isles: and, 3rd. 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. As a general rule, we may regard the most southern floras to be oldest, especially when, as in these cases, they are more and more fragmentary, and their character is more and more southern.
That which I have numbered III. is the most extensive, and from the number of species which are exclusively or chiefly found in chalk districts in this country, I have called it the Kentish flora. But the attachment of such plants to chalk is an accident, and not an essential habit of the species; the preference is simply for calcareous districts. In other countries they are found indifferently on most forms of limestone, and on calcareous sands and clays. Botanists who write of such and such plants being present because the chalk is present, forget that, unless they be species peculiar to the locality examined, they must owe their presence to diffusion from some other, since chalk of itself has no power to call up any species, by an equivocal or spontaneous generation of it And when a so-called chalk plant is not found on limestones adapted to it beyond (in our case, north of) the chalk, we must attribute its absence rather to geographical causes and impediments to its extension in that direction. This flora is evidently derived from the north-western provinces of France, and as no geologist doubts the ancient union of the two sides of the Channel, the course it pursued in migrating to England is sufficiently obvious. The epoch of the formation of the Straits of Dover would mark the period of its isolation, and if that breach of continuity was effected before the destruction of the great Germanic plain, as is probable, we may regard the Kentish flora as very ancient. Still more ancient appears to have been the flora numbered II., the ​peculiarities of which are seen more especially in Cornwall and Deron, and in the south-east of Ireland. This flora—a relic of a larger—is undoubtedly a part of that which we find in the Channel Isles, and in the adjacent provinces of France. It is still more southern in character than No. III., exhibiting the features of the transition between the great flora of central Europe and that of the southern or Mediterranean region.
When we look to the geological features of the districts occupied by this Devon or Norman flora, we see that its course is marked by the remains of a great barrier, the destruction of which probably took place anterior to that of the formation of the higher and narrower parts of the Channel. It marks, too, the course of the southern bound of the glacial sea.
But whilst I incline to the view that the Kentish and Devon floras are anterior in migratory origin to the Glacial and Germanic, yet I do not press it as essential. For since the Straits of Dover could not have been opened out until the destruction of the greater and all the central part of the Germanic plain, it might fairly be held by those who may object to the survival of the two floras in question, when bounding the glacial sea, that their migration was coeval with the Germanic migration; that the English Channel is of post-pliocene origin, and that the great Devonian barrier was not destroyed until the close of the Glacial period. The holders of such a view would, of course, reduce the epochs of migration to three, instead of five. Such a view would not in the least aflect the general truth of my theory.
Whatever doubts may be entertained respecting the antiquity of the Kentish and Devon floras, there can be none (if my premises be granted) respecting that which I have numbered I., and from which the peculiar botanical character of the south-west and west of Ireland is derived. The number of species included in it does not reach a score, but most of them play an important part in the mountain vegetation of the region. The remarkable point concerning these plants (for as yet no terrestrial animals of this period have been noticed, nor from what I shall presently have to say is it likely there are any now existing) is that they are all species which at present are forms either peculiar to or abundant in the great peninsula of Spain and Portugal, and especially in Asturias. No existing distribution of marine currents will account for their presence, and even if there were plausible grounds for attributing it to the great current known as Rennel's which sweeps the northern coasts of Spain, and strikes in its after-course against the western shores of Britain and Ireland, the plants in question, instead of being where they are, should be present in the southern districts of the countries bounding the English Channel,—in the region of the Devonian flora, where they are not. Nor can we suppose that ​they have been conveyed as seeds through the air; for besides the un- portant fact that they are all members of families having seeds not well adapted for such diffusion, and that the species of Compositæ and other plants with winged seeds associated with them in Spain are not present with them in Ireland, it would be very extraordinary if the winds which had conveyed them so far, had never, through, probably a long series of centuries, conveyed them still further, and diffused them in a country where there are abundance of situations well adapted for their habitation. The hypothesis, then, which I offer to account for this remarkable flora is this—that at an ancient period, an epoch anterior to that of any of the floras we have already considered, there was a geological union or close approximation of the west of Ireland with the north of Spain; that the flora of the intermediate land was a continuation of the flora of the Peninsula; that the northernmost bound of that flora was probably in the line of the western region of Ireland; that the destruction of the intermediate land had taken place before the Glacial period; and that, during the last-named period, climatal changes destroyed the mass of this southern flora remaining in Ireland, the survivors being such species as were most hardy, saxifrages, heaths, such plants as Arabis ciliata and Pinguicula grandiflora, which are now the only relics of the most ancient of our island floras.
This, I admit, is a startiing proposition, and demands great geological operations to bring about the required phenomena. With such a gulf as now intervenes between Ireland and Asturias it may seem fanciful and daring to suppose their union within the epoch of the existence of the plants now living in both countries. What then are the geological probabilities of the question?
During the epoch of the deposition of the miocene tertiaries there was sea—probably shallow—inhabited by an assemblage, almost uniform, of marine animals throughout the Mediterranean region (tertiaries of Cerigo, Candia, Malta, Corsica, Malaga, Algiers), across the south of France (Montpellier, Bordeaux), along the west of the Peninsula (Lisbon, &c.), and in the Azores (St. Mary's). I speak to the uniform zoological character of this sea from personal examination of its fossils. During the miocene epoch, then, we can suppose no union of Asturias and Ireland. But at the close of the miocene epoch great geological operations took place: witness the miocene marine beds discovered by Lieut. Spratt and myself at elevations from 2 to 6,000 feet in the Lycian Taurus. The whole of the bed of this great miocene sea appears to have been in the central Mediterranean and west of Europe pretty uniformly elevated. This then could—with every probability—have been the epoch of the connexion or approximation of Ireland and Spain. My own belief is, that a great miocene land, bearing the peculiar flora and fauna ​of the type now known as Mediterranean, extended far into the Atlantic—past the Azores—and that, in all probability, the great semicircular belt of gulf-weed ranging between the 15th and 45th degrees of north latitude, and constant in its place, marks the position of the coast-line of that ancient land, and had its parentage on its solid bounds. Over this land that flora, of which we have now a few fragments in the west of Ireland, might with facility have migrated. This would give us a new antidate, and enables us to declare our entire existing terrestrial flora and fauna as post-miocene.
The fact that there is a well-marked belt of miocene coast-line in North America (as shown by Mr. Lyell), and that the mollusca of that belt, as I have convinced myself from personal examination, indicate a representatiye, not identical, fauna in that region proves that during the miocene period there was an Atlantic gulf separating the new world ​from the old, and favours the notion that the coast-line of a post-miocene European land would be somewhere in the central Atlantic, about the position of the great Fucus Bank. The probability of the ancient existence of such a land is further borne out by the fact that the floras of the groups of islands between the gulf-weed bank and the mainland of the Old World are all members of one flora, itself a member of the Mediterranean type, and only peculiar inasmuch as certain endemic species are present, many of which are common to the Azores, Madeira and the Canaries.
Having broached these views at the late Cambridge meeting of the British Association, I have had an opportunity of hearing and considering such objections as have been offered against them. Such as have been offered against the premises assumed, are sufficientiy met by the preliminary observations on specific centres, which are also equally applicable to a proposition which has been made to account for the peculiarities of the British floras, by transmutation from marine into terrestrial species within given areas, though a knowledge of the submarine vegetation of the areas in question would have prevented such hypothesis ever having been broached. A more serious objection is that which asserts that a more extended view of the distribution of animals and plants will, so far from supporting, offer numerous difficulties to the theory which I have brought forward to account for the origin of our British fauna and flora. These, however, I have well considered, and have not as yet found any which at all invalidate my views, but, on the contrary, to render probable their general application. 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.
My main position may be stated in the abstract, as follows:—
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.
The question of the general origin of alpine floras and faunas is, perhaps, the most important inquiry which such a position can affect, and may be regarded, in a great measure, as a fair test of its truth. If the ​view I have put forward respecting the origin of the flora of the British mountains be true—and every geological and botanical probability, so far as that area is concerned, favours it—then must we endeavour to find some more plausible cause than any yet shown, for the presence of numerous species of plants, and of some animals, on the higher parts of alpine ranges in Europe and Asia, specifically identical with animals and plants indigenous in regions very far north, and not found in the intermediate lowlands. Tournefort first remarked, and Humboldt, the great organizer of the science of natural-history geography, demonstrated, that zones of elevation on mountains correspond to parallels of latitude, the higher with the more northern or southern, as the case might be. 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. In reality, the former essentially depend on the law, the latter being an accident not necessarily dependent upon it, and which has hitherto not been accounted for. 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. In the case of the Alps and Carpathians, and some other mountain ranges, we find the law maintained partly by a representative flora, special in its region, i. e., by specific centres of their own, and partly by an assemblage more or less limited in the several ranges of identical species, these latter in several cases so numerous that ordinary modes of transportation now in action can no more account for their presence than they can for the presence of a Norwegian flora on the British mountains. Now, I am prepared to maintain, that the same means which introduced a subarctic (now mountain) flora into Britain, acting at the same epoch, originated the identity, so far as it goes, of the alpine floras of middle Europe and central Asia. For now that we know the vast area swept by the glacial sea, including almost the whole of central and northern Europe, and belted by land, since greatly uplifted, which then presented to the water's edge those climatal conditions for which a subarctic flora—destined to become Alpine—was specially organized, the difficulty of deriving such a flora from its parent north, and of diffusing it over the snowy hills bounding this glacial ocean, vanishes, and the presence of identical species at such distant points remains no longer a mystery. ​Moreover, when we consider that the greater part of the northern hemisphere was under such climatal conditions during the epoch referred to, the undoubted evidences of which have been made known in Europe by numerous British and Continental observers, on the bounds of Asia by Sir Roderick Murchison, in America by Mr. Lyell, Mr. Logan, Captain Bayfield, and others; and that the botanical (and zoological as well) region essentially northern and alpine, designated by Professor Schouw that "of saxifrages and mosses," and first in his classification, exists now only on the flanks of the great area which suffered such conditions; and that, though similar conditions reappear, the relationship of alpine and Arctic vegetation in the southern hemisphere with that in the northern is entirely maintained by representative and not by identical species; (the representation, too, being in great part generic, and not specific), the general truth of my explanation of the origin of alpine floras, including identical species, becomes so strong, that the view proposed acquires fair claims to be ranked as a theory, and not considered merely a convenient or bold hypothesis.
Assuming as well founded the origin and general diffusion during the glacial epoch of a flora and fauna of subarctic and Alpine type throughout the northern and central regions of the old world, an important corollary follows, respecting the relative antiquity of the flora and fauna now general throughout the British Isles (which I have termed the Germanic), derived by migration over the upheaved bed of the glacial sea, from the central regions of Europe, viz.,—that the Germanic fauna and flora, equivalent to a part of the second botanical province in Professor Schouw's arrangement, not only migrated at a later epoch, but also originated later in time than the Scandinavian flora, which now clothes the summits of our mountains.
If the views I have ofiered respecting the origin and distribution of our terrestrial fauna and flora be correct, we might expect to find evidence in their favour when we inquire into the distribution of the marine plants and animals now inhabiting the British Seas. Especially ought we to discover important facts bearing upon the soundness of the propositions respecting the origin of our alpine flora, for we have already seen that the conversion from a general flora, clothing most parts of the area as were then above water, into a limited assemblage of plants almost all confined to the mountain summits, was owing to an elevatory action by which the bed, or a great part of the bed of the glacial sea, was left high and dry. The remains of that ancient sea bottom, in the form of stratified and unstratified masses of clay, sand, and gravel, often including large boulders, and presenting in many places considerable thickness and superficial extent; are to be met with in many parts ​of Great Britain and Ireland. In those beds we find fossils, and as these fossils are the remains of animals coeval, if my theory be true, with the existing flora of our mountains, an examination of them ought to afford a good test of its correctness.
Before, however, inquiring into this matter, let us take a general glance at the botanical and zoological features presented by the British seas. A correct knowledge of these, and even in certain departments of their details, will be absolutely necessary to any geologist who hereafter may engage in one of the most interesting inquiries in British geology, as yet but very imperfectiy handled,—the history of the northern drift and boulder clays.
The marine flora is of much less importance, as bearing upon these inquiries, than our marine fauna. For as almost all (Zostera and Zanichellia are exceptions) of the plants inhabiting our seas are cryptogamic, and marine cryptogamia seem to be far more widely diffusable, owing to the organization, transportability, and persistent vitality of their germs (spores)—and also to the capacity of cryptogamic plants to endure great vicissitudes of climatal conditions—their zones of distribution are not nearly so definite as those of most seed-producing plants, and a great number of species are cosmopolitan. Thus there are species of Ulva, Enteromorpha, Codium, and other genera, which seem to have an universal distribution, extending from pole to pole, and diffused through both hemispheres. As a general rule, however, the higher the algue, the more limited in distribution; and well marked, though wide algological regions have thus been traced out by botanists. The observations of Lamouroux, that the diffusion of algæ is determined by lines of coast and depth of water, shows that even their distribution has been mainly determined by geological events; and ere long, when it shall have been studied with reference to the latter, I do not doubt we shall gain new and unexpected information respecting the causes which have arranged them in the sea as they now are. From the researches of Dr. Greville, Mr. Harvey, Mrs. Grrifith, and other British algologists, it appears that our marine vegetation presents at least two well-marked types; a southern and a northern, both perhaps admitting of minor subdivisions. Thus the genera Padina and Halyseris do not range further north than the south coast of England, and are met with only in few localities there; and the genera Cystoseira, Sporochnus, Elaionema, Cutleria, certain species of Dictyota, Sphacelaria, Mesogloia, Rhodomenia (R. bifida, R.jubata) and Gigartina, all aid in marking out a southern region, which includes the British Channel, and part of the east coast, the Bristol Channel and the south and west of Ireland. The absence of southern species, the greater abundance and luxuriance of northern forms, and the presence of such fuci as ​Odonthalia dentata, Rhodomela cristata and lycopodioides, and Fucus Mackaii in like manner characterize a northern flora on the coasts of Scotland and of the north of England and Ireland.
The fauna of our seas, like the flora, presents distinct northern and southern relations. These are especially manifest among the Invertebrate animals, and also among the fishes. The few marine Mammalia included in the British list, are mostly derived from northern regions though some, as Phoca vitulina and Delphinus phocæna are constant and characteristic residents. Phoca barbata and Delphinus melas may be regarded as representatives of a Boreal type and Trichechus rosmarus, Delphinus albicans, Monodon monoceros, Balæna mysticetus and Balænoptera boops and rostrata as arctic forms, wandering to the limits of their range. Some of the larger Cetacea appear to have been more frequent visitors to our shores anciently—even during historical times—than now. The marine Reptilia represented by Sphargis coriacea and Chelonia imbricata are members of a southern type, and visitants from an opposite direction to that whence we have obtained our aquatic mammals.
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.
The occasional visitants of the south-western coasts of England indicate that the southernmost parts of our islands are not far from the northern bounds of the great province of south-European fishes, a region of which the coasts of the Peninsula may be regarded as the centre, and the Mediterranean as in a great measure an extension eastwards. To this province belong many of our rarities, such as Serranus cabrilla, Serranus gigas, Mullus barbatus, Pagrus vulgaris, Pagellus erythrina, Dentex vulgaris, Labrus iulus, Muræna helena and Ophidion imbarbe. ​Such can scarcely be regarded as true members even of our southern-most ichthyological fauna, of which are rather characteristic Zeus aper, Trigla pini, Pagellus centrodontus, Cepola rubescens, Atherina presbyter, Blennius ocellaris, Cantharus griseus, Trygon pastinaca and Clupea pilchardus; the last, though found on most parts of our coast, being only prevalent in the south-west.
In like manner our northenmost ichthyological province includes at its extremity occasional visitants which there reach the south-eastern limit of their range, as Cottus quadricornis, Scorpæna Norvegica, Gymnetrus arcticus, Scymnus borealis, Chimæra monstrosa and Brosmus vulgaris; the two latter are constant and the last an abundant inhabitant of the Zetland Seas. Certain species also, which though they range throughout our seas, are only abundant in the north, may be regarded as true members of this province—as Anarrhicus lupus, Merlangus carbonarius, Cyclopterus lumpus and Myxine glutinosa, and even the cod (Gadus Morrkua), and the herring (Clupea harengus).
The assemblage of fishes, of which the British Seas may be regarded as the centre, is partly composed of species which are not known elsewhere, and therefore essentially of a British type and partly of such as are characteristic of the seas bounding the shores of the central portion of Western Europe, and which may be styled the Celtic region. That great extension of sub-marine land surrounding the British Isles, a map of which has been given by Sir Henry De la Beche, in his 'Researches in Theoretical Geology' (where the important bearing of such a tract on many geological phenomena is admirably explained), may be regarded as the true country of the Celtic sub-marine fauna, of which such fishes form a part. Leptoœphalus Morrisii, Lepadogaster cornubiensis, Liparis Montagui, Clupea alba, and Raniceps trifurcatus are examples of the first or British division of this type, whilst a host of species, including Trigla gurnhardus, Cottus bubalis, Aspidophorus cataphractus, Scomber scomber, Blennius pholis, Crenilabrus tinca, Merluchius vulgaris, Lota molva, Solea vulgaris, Pleuronectes maximus and rhombus, Anguilla conger, Ammodytes tobianus and lancea are well-known members of the second.
To the oceanic type belong such of our occasional visitors as have very wide ranges, as Naucrates ductor (the pilot-fish), Echineis remora (the sucking fish), Trichiurus leptura, Xiphias gladius (the sword fish), Scomber pelamys (the bonito), and many of our sharks.
The marine Articulata of the British Seas have been so little studied, so far as their distribution is concerned, that it is difficult to give even the slightest sketch of it. Materials, however, are gradually accumulating, and so far aa the Crustacea are concerned—the division most importtant to the geologists, sedng that their remains are often preserved in ​upheaved strata—this defect will be in a great measure remedied by the completion of the 'History of British Crustacea,' by Professor Bell, now in the course of publication. Before the appearance of that work Mr. W. Thompson's 'Report on the Irish Fauna' was the only sound authority. The 'Catalogue of British Annellides' lately published in the 'Annals of Natural History,' by Dr. Johnston, has given us a firm basis on which to found our researches in that difficult department: but the distribution of European Annellides—a most interesting subject—is at present a blank in zoological science. We have every reason to believe that both marine worms and Crustacea exhibit a distribution on our shores very correspondent to that ascribed to the fishes. Thus among the higher Crustacea an extreme southern type is indicated by such forms as Macropodia tenuirostris and Pisa gibsii, and certain other species confined as British to the south-western parts of the Channel:—a southern British type by Maia squinado, Pinnotheres pinnæ, Achæus cranchii and Lithodes maia:—a Celtic and central British type by Macropodia phalangium, Inachus Dorsettensis, Hyas araneus, Portumnus variegatus, Pinnotheres pisum and species of Ebalia and Pagurus—a northern, by Nephrops norvegicus, Porcellana platycheles, and species of Alauna and Cuma—and an oceanic or general North Atlantic, probably by Pagurus Bernhardus, Homerus vulgaris and Palæmon serratus. Among the Cirrhopeda too are found Balanus scoticu—important, as will be seen hereafter, in a geological point of view—characteristic of the northern portion of our seas, and Acasta Montagui of the southern, whilst the pedunculated forms are, with the exception of Scalpellum vulgare, either oceanic and prevalent on the ocean side of our islands, or species introduced by their habits of adhering to the sides of ships and to floating wood. 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. When we consider the perfect state in which the testaceous species are preserved, and the facility of specific identification afforded by their shells, this becomes of great importance. 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. Valuable materials have, however, been collected in the larger works of Montagu, Turton, and Fleming, and in many essays on local faunæ, among which, the Report of Mr. W. Thompson 'On the Irish Invertebrata,' published in the Transactions of the British Association for 1843, and prepared at the request of that body, is by far the most important. The following sketch of the distribution of marine Mollusca on the British shores, is offered as a brief summary of the results, chiefly of my own obsenrations.
I. In the southern part of the British Channel, we find certain species which haye there the northernmost limits of their range. Such are Haliotis tuberculata, which, abundant in the Channel Isles, is not indigenous on our own shores, Emarginula rosea, occasionally taken on the south coast of England, but frequent on the coast of Guernsey, Truncatella Montagui, Rissoa Bryerea, denticulata and calathisca, Calyptrea sinensis, Donax complanata, Lucina pisiformis, Galeomma Turtoni, Pandora rostrata, and Lithodomus lithophagus. These species mark the bounds of a fauna which can scarcely be regarded as within our limits.
II. Some of them, howeyer, are occasionally found alive on our southern shores, and on the south and south-west of Ireland, associated with a number of species which constitute a well-marked South British type. Such are Avicula atlantica, Modiola Gibsii, Venus verrucosa, aurea and chione, Venerupis irus, Arca lactea, Cardium tuberculatum, Pholas dactylus and lamellata, Volva patula, Pleurotoma gracilis, Trochus exasperatus, striatus and crassus, Adeorbis subcarinatus, Rissoa striatula and auricularis, and Pollia minima. This fauna stretches far up on the coast of Ireland, occupies St. George's Channel, having its northern limits about the line of Cardigan Bay, and is generally distributed through the English Channel, even to the entrance of the German Ocean.
III. There are certain species very generally diffused throughout the seas and shores of the British Isles, and which range generally through the European Seas, or at least along the coasts of Western Europe, from Norway to the south of Spain. Such constitute an European type. Such are: Turritella terebra, many Rissoæ (as, R. striata, cingilla, parva, interrupta, ventricosa, fulva), Odostomia plicata, Trochus magus, ziziphinus, tumidus, cinerarius, several Pleurotomæ, Aporrhais pespelecani, Cypræa Europæa, Tornatella fasciata, Natica Alderi, Dentalium entalis, Patella vulgata, Emarginula fissura, Chiton fascicularis, Capulus hungaricus, Ostrea edulis? Pecten opercularis, Nucula nuclea, Modiola marmorata, Cardium edule, lævigatum and echinatum, Donax trunculus, Tellina donacina, tenuis, and fabula, Abra Boysii, Mactra stultorum, Kellia suborbicularis, Artemis exoleta and lincta, Venus ovata, fasciata, and gallina, Pullastra virginea, Corbula nucleus, and Psammobia tellinella. ​Most of the above-named species are very prolific, several being gregarious. An important point respecting them is the fact, that they are all confined to the eastern coasts of the Atlantic. The application of this fact will be seen hereafter.
IV. As plentiful in our seas as the species constituting the European type are many forms, the relations of which are rather northern than southern, but their chief development within and around our area. These constitute the Celtic type. Such are, Bulla lignaria, Skenea depressa, Littorina littorea, rudis, and neritoides; several species of Lacuna, Nassa reticulata and macula, Purpura lapillus, Buccinum undatum, Fusus antiquus, Triton erinaceus, Natica monilifera, Patella pellucida, and lævis, Lottia virginea, Chiton marginatus, Pecten maximus, Pectunculus pilosus, Modiola vulgaris, Abra prismatica, Mactra solida, and subtruncata, Astarte danmoniensis, Venus cassina, Pullastra vulgaris, Pandora obtusa, Mya truncata and arenaria, Solen siliqua and ensis, and Saxicava rugosa. Several of these are common to the coasts of Europe and of North America. Such species have invariably a continued range north of Britain, and with two or three exceptions cease before they reach the Mediterranean.
V. In the British Seas are a number of species not known elsewhere, or else very rare on other coasts. These are mostly found in the Irish Sea, which appears to have been the centre from which they have radiated. They constitute a peculiarly British type: Chemnitzia fulvocincta, and some allied species; several Rissoæ and Odostomiæ, Skenea serpuloides and divisa, Trochus umbilicatus, Montacuti, and millegranus, Scalaria Turtoni and Trevelyana, Velutina otis, and Natica Montagui, may be cited as examples; and such bivalves as Pecten sinuosus and obsoletus.
VI. In Dr. Fleming's History of British Animals—a work the original merits of which have scarcely yet been done justice to—the range of a great number of spedes of British Mollusca is summarily stated as "from Devon to Zetland." Many of the forms thus noted, are rarely, if ever, found in the Irish Sea or in the German Ocean. Nevertheless, the note of range is quite true, and founded on the personal observations of Dr. Fleming in the Zetland Isles and north coast of Scotland, as compared with those of Montagu on the south coast of England. The Mollusca, and other animals alluded to, are not generally distributed throng the British Seas, and are mostiy of southern origin (or members of the South European fauna). They are not grouped in patches far apart, but have a continuous distribution, which, commencing at the south-western shores of England, is extended across the southern part of St George's Channel, is continued along the west coast of Ireland, round to the Hebridean Isles, and even northwards to the Zetland Seas. Thus, the species, among which are ​many of the forms common to the British and Mediterranean Seas, are mingled in their course with forms characteristic of the Celtic, Boreal, and sub-Arctic regions; and nothing but the most minute examination and the active employment of the dredge, and registering of its contents, could have cleared up the confusion which this peculiarity in the distribution of the fauna of our western shores, bordering the Atlantic, threatened to introduce into all our calculations.
This portion of our fauna, which for convenience I will term the Atlantic type, to distinguish it from the Oceanic, we see exemplified in such species as, Bulla cranchii, Eulima polita, Eulima subulata, Littorina cœrulecens, Rissoa cimex, R. costata, Scalaria Treveliana, and clathratulus, Cerithium lima, Triphoris adversus, Pleurotoma attenuata, linearis, purpurea, gracilis, Erato lævis, Terebratula caput serpentis? Pecten lævis, Lima tenera? Lima subauriculata, Arca tetragona, Cardium elongatum? Lucina spinifera, Circe minima, Pullastra decussata, Solenecurtus candidus, and antiquattis, Psammobia florida (vespertina, Turt. non Lam.) and Gastrochæna pholadia.
VII. On the same coasts with these species are taken the mollusks of an Oceanic type, mostly occasionally visitors drifted hither by storms from the west and south. Such are Spirula Peronii, which has several times been cast up on the west coast of Ireland, Ianthina communis, nitens, and exigua, Hyalæa trispinosa, and possibly Peracle Flemingii. With these we may expect some day to find other species of Pteropoda. The various species of Anatifa among the cirrhipeds, and of Velella and Diphyes among our Medusæ, included in our fauna, are members of the same type.
VIII. The coasts of Scotland, and the neighbouring parts of England and Ireland furnish the cabinets of conchologists with many species which are very rare or almost unknown on the English shores. Some of these are confined to the east coast, some to the west, but the greater number are common to both. Such are, Pecten niveus, nebulosus and striatus, Nucula tenuis, minuta and pygmæa, Crenella decussata, Modiola nigra, Cardium Löveni, Abra intermedia, Astarte elliptica and compressa, Cyprina islandica—found everywhere on our shores, but abundant only in the north—several species of Neœra, Panopæa arctica, Margarita communis and striata, Trichotropis borealis, Fusus Barvicensis, Bamfius, and Norvegicus, Velutina lævigata and ovata, Natica helicoides, Lottia ancyloides, testudinaria and fulva, Emarginula crassa, Cemoria noachina, Chiton Hanleyi, Crania Norvegica, and Terebratula caput serpentis. Most of these species are found also on the Scandinavian shores, and several of them are common to the North American and North European Seas. They constitnte my Boreal type, the province of which extends northwards, from the northern shores of the Isle of Man and Ireland, on ​the one side, and from the central portion of the German Ocean on the other.
IX. Found rarely south of the most northern of our seas, and for the most part rare even there, are certain species which mark the near approach of an Arctic or sub-Arctic province. Such are, Margarita undulata, Natica groenlandica, Fusus albus and Sabini, Buccinum Donovani, Astarte borealis, and Terebratula cranium. They are associated with zoophytes of equally Arctic character. Many of the species enumerated under the last type are much more abundant, and finer, in the northernmost province, of which they are truly members—their distribution southwards being occasional and in isolated patches, the nature of which I shall hereafter explain.
Our native Radiata have a similar distribution with the Mollusca, though, perhaps—owing to the great powers of locomotion which many of them possess, either in their perfect or else in their larva state—not so well marked. The coral Turbinolia milletiana (discovered by Mr. MacAndrew, alive, off the Cornish coast, hitherto known only as fossil) and the Echinus lividus, Thalassema Neptuni, and Syrinx nudus, are examples of the southernmost types. Comatula rosacea, Ophiura texturata and albida, Ophiocoma rosula and neglecta, Uraster glacialis, Palmipes membranaceus, Asterina gibbosa, Asterias aurantiaca, Echinocyamus pusillus, Spatangus purpureus, Cucumaria pentactes, and Syrinx nudus, among the Echinodermata, and Pennatula phosphorea, Alcyonium digitatum, Actinea effæta, Laomedea gelatinosa, Sertularia pumila and many hydroid zoophytes, Cellepora pumicosa, Tubulipora serpens, and many ascidioid zoophytes, are representatives of the third or European type. So also are such Medusæ as Aurelia aurita and granulata.
The Celtic type is seen in Uraster rubens, Solaster papposa, Echinus sphæra and miliaris, Amphidetus cardatus and roseus, Thyone papillosa and Echiurus vulgaris, Actinea mesembryanthemum, senilis and dianthus, Flustra foliacea, Antennularia antennina, Plumularia falcata, and many Sertulariæ and other hydroid and ascidioid zoophytes.
The British type is represented by Ophiocoma brachiata, and minuata, Uraster hispida, Syrinx Harveii, several corneous zoophytes, as, Thuaria articulata and Plumularia myriophyllum, Actinea bellis, Anthea tuediæ, Capnea sanguinea, Iluanthus scoticus? Cellepora Skenei, and many other ascidioid zoophytes. I doubt whether any of our Medusæ come properly under this head.
The Atlantic type is represented by certain zoophytes, among which are Carophyllia Smithii, Plumularia pennatula, and Eschara foliacea.
The Oceanic type is instanced by such Medusæ as Velella and Diphyes, occasional visitants of our western shores.
The Boreal type has numerous members among the Radiata. ​Echinoderms, Ophiocoma granulata and bellis, Goniaster pulvillus (Templetoni), Echinus Flemingii? Brissus lyrifer, Psolus phantapus, Cucumaria frondosa, Thyone raphanus, and other Holothuriadæ, are good examples; as are the species of Beroë and Alcinoë, among the Acalephæ. Of zoophytes Virgularia mirabilis, and other species frequent only in the northern coasts of Britain, belong to this type, as also do several sponges.
The sub-Arctic type is well marked in the Zetland Seas by the presence of several Radiata which do not range farther south; such as, Echinus neglectus, Cidaris papillata, Echinarachneus placenta? Lucernaria fascicularis, ,,Actinea intestinalis, Oculina prolifera, Primnoa lepadifera, Astrophyton scutatum, Priapulus caudatus, Corymorpha nutans, Flustra setacea, and Tethya cranium.
I have dwelt thus fully on the distribution, horizontally, of British marine animals, because a knowledge of it is of the greatest importance to the geologist who directs his attention to the phenomena presented by tertiary strata, not only within our own area, but throughout the northern hemisphere, and because the subject is one of which there is no connected view presented in any published work, whilst even the details of many parts are either not in print or scattered through many books, journals, and memoirs. In the first section of this essay, it was not necessary to do so when our flora and terrestrial fauna were concerned, as (especially of the former) the details are fully collected and combined in accessible and well-executed works. This is also the case with the marine vertebrata, but not as yet with the greater part of the invertebrate animals of our seas, whose remains, as will be seen hereafter, furnish an invaluable clue to the history of conditions, climatal changes, and changes in the distribution of submarine life, which preceded the historical epoch, and organized, as it were, the present state of things.
The ancient history of this fauna—so far as the area under discussion is concerned—may be clearly made out. The most ancient traces of existing species still inhabiting the British Seas are probably to be found as far back as the cretaceous epoch, when Terebratula caput serpentis, certain existing foraminifera identified by Ehrenberg), and possibly some deep-sea corals lived under similar conditions of depth with those which now determine their distribution. About these, however, there may still be doubts, and even about most or all of the forms identified with existing British species, found in strata of the eocene period, when the assemblage of inorganic and organic phenomena within our area was such as cannot be compared with that presented by it at present, though closely approximating the state of things in certain regions nearer the equator. The close of the eocene period was probably marked by such a change in the disposition of land and water in the ​region of western Europe, as to cause an almost entire disappearance of the then marine fauna.
In the lowest, or coralline crags, however, we have presented decided relations between our existing marine fauna and that which then occupied the area of the south-west of England. The number and state of preservation of the Mollusca, Radiata, Cirrhipeda and testaceous Annellida, found in that formation, enable a very complete comparison to be instituted; and the elaborate catalogues of Mr. Searles Wood, drawn up with the greatest care and judgment, furnish materials for our inquiry, such as are not often at the disposal of the palæontologist. From Mr. Wood's researches, it appears that out of above 340 species of testaceous mollusks, found in the coralline crag, 73 are now known living in the British seas; among these are 23 which are found fossil in the northern drift, or Newer Pliocene beds of Britain. With the exception of Trichotropis borealis and Lottia virginea, both northern forms, the remainder consists of such British species as chiefly range south of Britain, in almost every case extending to the Mediterranean. The coralline crag mollusks not now living in the British Seas are either extinct forms, or species now commencing their northernmost range south of Britain: with them is associated Cancellaria costellifer, only known fossil in Europe, but still liviqg on the northern shores of the United States. The zoophytes of the coralline crag present similar phenomena. Out of 57 species most carefully examined by Mr. Searles Wood, 18 or 19 are existing British forms: these are associated with polypidoms of a more southern character, including species of Balanophyllia, Cladocara, Fascicularia, Theanoa, Hornera, Lunulites, Fungia, &c., of which we have now no representatives in our seas.
In the Red Crag there are about 260 species of testacea, out of which 60 are now known alive in the British Seas, a larger proportion than in the coralline. 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. The number of zoophytes has gready diminished, 25 species only having been observed, 14 of which are existing in the British Seas. The number of southern forms has also greatiy diminished.
Among the comparatively few marine shells recorded as fossils of the Norwich or mammaliferous crag, we find some British or northern ​species not previously met with, as Tellina fabula and solidula, Donax trunculus, Astarte borealis, and Murex erinaceus. The data are, however, not sufficiently complete to enable us to say more than that the fauna of the epoch during which that deposit was formed presented general features of a decidedly mixed Celtic and northern character.
Putting the mammaliferous crag aside, it is evident that the "coralline" and "red" crags afford clear indications of a state of things in the seas in which they were formed, very distinct from that now presented by the seas surrounding the British Isles. Mr. Searles Wood's reference of the coralline crag fauna to a type comparable with that now presented by the assemblage of marine animals in the Mediterranean, or on the coast of Portugal, appears to me to come very near the true state of the case; and his observatitms on the subject, in the ninth volume of the Annals of Natural History, are well worthy the attention of geologists. The epoch of the red crag was evidently marked by a new set of conditions which materially changed the character of the fauna. The key to the problem presented by these must be sought for in the zoological phenomena exhibited by the remarkable strata known under the names of "Boulder clay," "Arctic or northern drift," "Pleistocene," or sometimes "Newer Pleiocene," and in some authors "post-tertiary," including (in part) the "Till" deposits, which for convenience I shall henceforth mention as glacial, or as beds of the glacial epoch. My chief purpose in drawing up this essay, is to assist in the elucidation of that most interesting and important formation—one which will engage much of the attention of the geological surveyors—by exhibiting the nature and value of the evidence afforded by organic remains found in those beds, and the bearing of that evidence on the history of animated nature within the area under examination by the Survey, immediately before and subsequent to their formation. This evidence has not hitherto been put in a tangible form, nor has it been fully appreciated except by very few geologists, of whom Mr. Smith, of Jordan Hill, was the first to endeavour inductively to work out in detail the many problems it involves, and to impress upon the geological world the variety and interest of the palæontological phenomena presented by the glacial beds in the northern districts of Britain and Ireland. There is now a great mass of evidence existing, scattered through books or known to a few and as yet unpublished—sufficient to enable us to present well-grounded generalizations.
Exactly a century ago, the attention of the greatest of modern naturalists was arrested by the zoological phenomena presented by the glacial beds in Sweden. In the course of his journey through Wast-Gota, in 1746, Linnæus visited Uddevalla, the very locality destined long after, to furnish Mr. Lyell with part of the materials for his celebrated essay ​on the 'Rise of Land in Sweden.' The account of Linnæus's journey was published (in Swedish) in 1747. The descriptions and figures of the Uddevalla fossils there given, appear to have escaped the notice of most subsequent writers. Professor Jameson, when noticing Mr. Lyell's paper in the 'Edinburgh New Philosophical Journal,' briefly directed attention to the observations of Linnæus. As they have not been referred to in any geological work with which I am acquainted, and as, from the accuracy of the information they contain, they must be regarded as among the most valuable of the published notes on the organic remains of the northern drift, as well as most interesting, on account of the time of their publication, and the man who recorded them, I avail myself of the kindness of my distinguished friend, Dr. R. G. Latham, to present a translation of the passage in the 'Wast-Gota Resa.'
"The shell hills (Skalbargen) are rightly reckoned amongst the greatest wonders of Bohuslaen; for they lie inland nearly a whole quarter of a mile, in some places, from the sea. These shell hills consist of periwinkles and bivalve shells (Snacke-och Muskle-skal), which are here assembled in such numbers, that one wonders how so many living beings existed on the earth. We visited Capell Hill, which lay a quarter of a mile beyond the southern Uddevalla Gate: then we went to Sammered, which lay nearly a quarter of a mile from the town, N.E. In both places were these shell-hills, especially and most markedly at Sammered. Here there were bare and hillocky ridges of gray stone, which, on the sides that front the town or the sea, where the bay was originally, bent in. The earth was slightly convex on the summits of the above-named hill, and made a curve; where the black mould, which was seldom more than a foot or a foot and a half deep, thinned off, the shell bed, which was two or three fathoms deep, underlaid it Under this came in succession pure clay. No shells were seen above this stratum among the bare hill ridges. They stretched, however, altogether from the hill downwards under the black mould, often to the breadth of several gunshots. The shells lay clean and unchanged, with no addition of soil, only strewn over with a little gravel, such as is thrown up on the beaches. I sought carefully for all the sorts of shell fish that were found here, in order that I might determine from what world they came, or if the sea, even as the land, had changed its inhabitants."
Linnæus then gives an enumeration of the species he found there, and figures the most remarkable. He notices the following: 1st. "Lepas quæ Balanus Uddevallensis."—Tab. v. fig. 1. This is our Balanus scoticus.
2nd. "Concha oblonga obtusa, sulcis transversis."—Tab. v. fig. 2. This is the large variety of the Saxicava rugosa, or Saxicava sulcata.
​3rd. "Concha lævis, altera tantum parte clusilis, apophysi admodum prominente lataque prædita."—Lister. Angli., 191, tab. v. fig. 36. The figure referred to in Lister, represents Mya arenaria.
4th. "Cochlea testa ovata, spiris quinque striatis fasciatis, aperturæ margine postero dilatato rotundato,—kupunge."—Lister, Angli., 162, tab. iii. fig. 9. The figure referred to in Lister is that of Littorina littorea.
5th. "Concha Mytilus dicta." Mytilus edulis.
6th. "Cochlea spiris quinque utrinque producta striis acutis imbricatis."—Tab. v. fig. 6. This is the well-known and characteristic glacial fossil, Fusus scalariformis, which, since Linnæus's time, has been over and over again described and figured as new, under difierent names.
7th. "Concha Pecten dicta striis numerosissimis."—Table v. fig. 7. This is the Pecten islajidicus, equally characteristic of these beds.
8th. "Cochlea spiris octo oblonga utrinque producta lineis duabus elevatis."—Tab. v. fig. 8. This is the subcarinated variety of Fusus antiquus.
9th. "Lepas concha anatifera transversim sulcata longitudinaliter striata."—Tab. v. fig. 9. This is Balanas sulcatus.
10. "Concha Pectunculus dicta (Fauna 1340)."
Sixty years after the observation of the fossils at Uddevalla, by Linnæus, they attracted the attention of the all-observing and philosophic Von Buch, who also noticed the occurrence of remains of existing testacea, in upheaved beds, in Norway. The presence of organic remains in similar beds in Scotland was noticed from time to time in the 'Memoirs of the Wernerian Society'—volumes which contain numerous valuable papers bearing upon the phenomena, both geological and zoological, of the glacial epoch. The Memoir of Mr. Lyell, on the Uddevalla deposits already referred to, published in 1836, gave a new impulse to the natural history part of the inquiry, from the invaluable list of fossils there given. The fruit of this in Britain, soon appeared in the researches of Mr. Smith, of Jordanhill, whose essays 'On the last Changes in the relative Levels of the Land and Sea in the British Islands,' published in the Memoirs of the Wernerian Society, for 1837-38, will ever be esteemed as the foundation of a critical investigation of this most interesting subject, in Britain; and I feel proud to acknowledge that my first insight into "Newer Pliocene" geology waa acquired through the instructions of that distinguished geologist, when accompanying him in one of his arduous but delightful journeys of investigation, in the Clyde district and north of Ireland. In the latter country, the phenomena of the drift had attracted the attention of many observers, among whom Dr. Scouler, Captain Portlock, Mr. Bryce, Mr. Griffith, ​and Mr. Hamilton, had remarked on the fossils it contained. More recently, Mr. Oldham has given lists of Irish drift fossils. (For the papers referred to, see 'Proceedings of the Geological Society of Dublin.') But by far the most valuable data on the fossil contents of the drift in Ireland—data which for importance as bearing on the questions of its origin and history, can be compared only with those collected by Mr. Smith and Mr. Lyell—have been brought together during the researches of this survey, by Captain James, R.E., Chief Geologist for Ireland, and will be made known in detail in the course of the Survey Reports. In Wales the fossils of the glacial beds were made known by Mr. Trimmer, who has done much to thrown light on their history. To him we owe the information respecting the presence of existing shells on the summit of Moel Trefaen. Mr. Strickland has published in the Geological Proceedings valuable and critical observations on the fossils in the Isle of Man beds, further information on which has been recently communicated to the Geological Society by the Rev. R. G. Cumming. The observations of the Rev. Mr. Landsborough (Geol. Proc., vol. iii. p. 444), on pleistocene beds in the east of Scotland are very valuable, from their minute accuracy, a quality without which no natural-history statements on this subject can be received as of any authority. To complete this brief notice of the zoological literature of the drift, we may enumerate Capt Bayfield's and Mr. Lyell's papers on the fossils in the Canadian beds, published in the Geological Transactions, the figures of drift fossils in Hisinger's 'Lethæa Suecica,' the papers of Dr. Forchhammer, the lists in Mr. Lyell's 'Travels in North America,' and the account of the fossils of the Russian drift, in Sir Roderic Murchison's great work on Russia, all containing data of the most accurate and valuable kind.
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. These beds attain various degrees of thickness, forming in places cliffs more than 100 feet high, and occupying various elevations above the sea, from 0 to more than 1000 feet. When carefully examined, most of them are found to contain fossils, mostly marine testacea, usually scattered, rolled and broken, but in particular localities, entire and undisturbed, and presenting undoubted evidence of their having lived and died on the spot. In such places they are abundant; when rolled and broken, usually dispersed, and in no great plenty.
I have personally examined these fossils in situ in most of the localities ​of the Clyde district, in company with, and under the guidance of Mr. Smith; in Wexford and Wicklow with Sir Henry De la Beche and Captain James, and alone in the Isle of Man, Cheshire, Lancashire, Anglesea, the north-east of England, the Forth district, and Caithness. For the statements herein made, I therefore hold myself responsible, and put them forth as the results of personal observation.
The total number of species of mollusca found in these beds in the British Isles, is about one hundred and twenty-four. With a few exceptions, they are all forms now existing in the British Seas. Nevertheless, they indicate a very different state of things from that now prevailing. As a whole, this fauna is very unprolific, both as to species and individuals, when compared with the preceding molluscan fauna of the red and coralline crags, or that now inhabiting our seas and shores. This comparative deficiency depends not on an imperfect state of our knowledge of the fossils in the glacial formations—on that point we now have ample evidence—but on some difference in the climatal conditions prevailing when those beds were deposited. 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. It is not the latitude, but the temperature which determines these differences. Hence we find the number of testacea inhabiting the east coast of America, between the parallels of 45° and 50° N., where the waters are climatally influenced by the currents from the Arctic Seas, ia much less than that assembled several degrees farther north on the coasts of Europe. In the following table, the number of testaceous mollusks of four well-ascertained faunas is contrasted with a summary of the testacea found fossil in the glacial formations of the British Isles. From it, it will be seen that the glacial molluscous fauna holds a numerical rank between
| ORDERS OF MOLLUSCA. | Comparative Table of Testacea inhabiting. | Comparative Table of Testacea inhabiting. | Comparative Table of Testacea inhabiting. | Comparative Table of Testacea inhabiting. | Fossil in British Glacial beds. |
| ORDERS OF MOLLUSCA. | The Medi- terranean. | British Seas. | Seas of Massa- chusetts. | Greenland Seas. | Fossil in British Glacial beds. |
| Cephalopoda, with shells................................................................................................................................................................................................................................................................................................................................................................................................ | 1 | 1 | 1 | .. | .. |
| Pteropoda................................................................................................................................................................................................................................................................................................................................................................................................ | 13 | 1 | .. | 2 | .. |
| Nucleobranchiata................................................................................................................................................................................................................................................................................................................................................................................................ | 6 | 1 | .. | .. | .. |
| Gasteropoda................................................................................................................................................................................................................................................................................................................................................................................................ | 368 | 248 | 100 | 74 | 60 |
| Lamellibranichiata................................................................................................................................................................................................................................................................................................................................................................................................ | 200 | 210 | 83 | 44 | 63 |
| Palliobranchiata................................................................................................................................................................................................................................................................................................................................................................................................ | 10 | 4 | 2 | 1 | 1 |
| Total................................................................................................................................................................................................................................................................................................................................................................................................ | 598 | 465 | 186 | 121 | 124 |
That the climate, under which the glacial animals lived, was colder, is borne out by an examination of the species themselves. We find the entire assemblage made up—1st, of species now living throughout the Celtic region in common with the Northern Seas, and scarcely ranging south of the British Seas; such are—
2nd. Of species which range far south into the Lusitanian and Mediterranean regions, but which are most prolific in the Celtic and Northern Seas; as—
3rd. Of species still existing in the British Seas, but confined to the ​northern portion of them, and mostly increasing in abundance of individuals as they approach towards the Arctic circle: such are,
Leda pygmæa (fossil in the newer pliocene deposits of Italy, Germany, and Britain, but taken alive and abundantly, by Mr. MacAndrew, who dredged it in 1845, in the sound of Sleye, where it is associated with boreal forms) belongs to this assemblage. It is identical with Nucula lenticula of Möller, from Greenland.
4th. Of species now known, living only in European seas, north of Britain, or in the seas of Greenland and Boreal America, as
5. Of species not now known existing, and unknown fossil in previous deposits.
6. Of species, fossil in the coralline or red crag, but still existing in the South-European though not in the British Seas.
Turritella incrassata.
7. Of extinct species, fossil also in the crag.
Tornatella pyramidata.
This fauna, then, is composed of living British species of northern origin, some of which are now confined to climates far colder than our own, with a few forms supposed to be extinct, and one or two shells of southern origin, or known only in the crag. It is important to observe that the latter are from the southernmost parts of these deposits in Ireland, where are also found members of the crag monstrosity of Fusus antiquus, known as Fusus contrarius, and the variety of Purpura lapillus, ​formerly termed Purpura incrassata. It is also of consequence to note the fact that the species most abundant, and generally diffused in the drift are essentially northern forms such as Astarte elliptica, compressa, and borealis, Cyprina communis, Leda rostrata and minuta, Tellina calcarea, Modiola vulgaris, Fusus bamfius and scalariformis, Littorinæ and Lacunæ, Natica clausa and Buccinum undatum; and even Saxicava rugosa and Turritella terebra, though widely distributed, are much more characteristic of north European than of southern seas.
I have elsewhere shown that among marine animals, zones of depth correspond to parallels of latitude, even as the latter are, in like manner, represented on land by zones of elevation. When I made known the facts proving this law, I did not distinguish between the law as really maintained by representative forms, and as apparently exemplified by identical species. This distinction I have pointed out in this essay when treating of alpine plants. It will be seen by and by that it is equally important to bear it in mind, in the case of the boreal forms of marine animals found at great depths in southern seas. The truth of the law itself, however, holds good, and the knowledge of its existence naturally leads us to inquire how far the apparently boreal or arctic fauna of the glacial beds might owe their climatal character to such a cause. This is an important question, for unless we can determine positively that depth was not the element to which the peculiar facies and numerical weakness of this submarine fauna were due, our climatal determinations, so far as they depend on zoological data, become mere hypotheses.
Fortunately, however, among the species enumerated are several which ought to afford us a certain clue to this matter. Such are the Littorinæ, the Purpura, the Patella, and the Lacunæ, genera and species definitely indicating, not merely shallow water, but in the three first cases a coast line. Were these shells only found among the disturbed and amorphous beds of drift, they would scarcely serve as evidence on so nice a point, since they might have been transported; but they occur also in the undisturbed fossiliferous clays of this formation, associated with bivalve and other moUusca of delicate conformation and in a state which certainly indicates that they lived and died on the spots where they now are found. This is especially the case among the Clyde deposits. A most important fact, too, is that among the species of Littorina, a genus, all the forms of which live only at water-mark, or between tides, is the Littorina expansa, one of the forms now extinct in the British, but still surviving in the Arctic Seas.
To make this evidence more clear, it is necessary briefly to notice the vertical distribution, or distribution in depth of existing mollusca in the British Seas.
​In an essay 'On the Associations of Mollusca on the British Coasts, considered with reference to Pleistocene Geology,' printed in 1840, I described the mollusca as distributed on our shores and seas in four great zones or regions, severally denominated "the Littoral zone," "the region of Laminariæ," "the region of corallines," and "the region of corals." An extensive series of researches, chiefly conducted by the members of the committee appointed by the British Association to investigate the marine zoology of Britain by means of the dredge have not invalidated this classification, and the researches of Professor Löven in the Norwegian and Lapland Seas have borne out their correctness. The first two of the regions above mentioned had been previously noticed by Lamouroux, in his account of the distribution (vertically) of seaweeds; by Audouin and Milne Edwards, in their 'Observations on the Natural History of the Coast of France,' and by Sars in the preface to his 'Bagtivelser og Jagtivelser.' The Littoral distribution of mollusks has firequently attracted the attention of zoologists. An admirable essay on the fauna and flora of the Littoral and Laminarian zones on the coast of Denmark has recently been published by M. Oersted.
The first, or Littoral zone, is that tract which lies between the high and low water marks, and therefore is very variable in extent, depending for its dimensions on the amount of rise and fa11 of the tides. In all parts of the northern hemisphere it presents very similar phenomena when its animal and vegetable inhabitants are examined, whether it be only a few inches broad, as in the Mediterranean, or beyond 30 feet in vertical extent, as in some more tidal seas. Throughout Europe, wherever it consists of rocky it is characterized zoologically by species of Littorina, botanically by Corallina; where sandy, by the presence of certain species of Cardium, Tellina and Solen; where gravelly, by Mytilus; where muddy, by Lutraria and Pullastra.
In the British Seas its inhabitants vary in the northern and southern districts, but there are many species constant throughout, both of plants (as the species of the genera Fucus, Lichina, Laurencia and Corallina), and aninoals (as Littorina rudis, littorea and neritoides, Purpura lapillus, Patella vulgata, Cardium edule, Kellia rubra, and many Annellides and Zoophytes, never found out of this region). This zone is itself divisible into several distinct sub-regions as well defined by characteristic animals and plants where it is narrowest as where it is broadest. To show that this assertion of the constancy of even the sub-divisions of the littoral zone is not put forth vaguely, but from minute observation (which is equally true in regard to the statements respecting the other zones in depth), I append a table exhibiting the characteristic animals and plants ​of the several littoral sub-regions, as noted by myself at six British localities, three northern and three southern, each presenting a different condition of sea-bottom, and considerable variation in amount of rise and fall of tides. In the first column I give the distribution as observed at Sandwick, on the east coast of the mainland of Zetland, where the fall of the tide is very small, and the shore composed of steep rocks of gneiss. Extremely unfavourable as such a locality must be to animal and vegetable life, we see, nevertheless, that such species as do occur take their respective places with as much deference to right of prece- dence as in the more favoured localities with which it is compared. The second and third exhibited the littoral distribution as observed at Armadale, in the sound of Skye, at one point on rock (old red sand- stone), at another in a shingly bay. The presence of Lottia testudinaria in this column is a feature indicative of the Boreal type of the fauna. The fourth column exhibits the distribution as noted on lime- stone at Slade, on the sea-side of Hook-point, the southern extremity of the county of Wexford; and the fifth, on the old red sandstone coast in the same district. In both these we see evidences of a more southern fauna in the presence of Trochus crassus, a characteristic species of the South British type of our native mollusca, whilst the occurrence of Trochus umbilicatus here, as well as in the Armadale column, is characteristic of the western seas of Britain generally. In the Zetland and Armadale columns the Spirorbis marks a zone much more distinctly than in those of the southern localities. The sixth column is an incomplete (in consequence of the time of tide) note of the distribution on a Silurian rocky shore at Tramore, in the county of Waterford. In all these columns the several members of each sub-region are to be understood as intermingled, except when it is expressly stated to the contrary; and several of the members of the third and fourth sub-regions occasionally stray into the first and second. 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.
The importance of a knowledge of the characteristic features of the littoral zone, to the geologists investigating the northern drift, cannot be too strongly enforced, seeing that the evidences of them presented by fossils are the surest tests of ancient coast lines, and guides to the determination of the amount of elevation, or depression, and direction of action of the disturbing force.
The second, or Laminarian zone, is that land-encircling belt which commences at low water mark, and extends to a depth of from seven to fifteen fathoms. The great tangle seaweeds form miniature forests in ​
| Divisions of Littoral zone. | Sandwick, E. of Zetland, on steep rocks of gneiss. Vertical extent four feet. | Sandwick, E. of Zetland, on steep rocks of gneiss. Vertical extent four feet. | Near Armadale, W. coast of Skye. Shingle and Sand. | Near Armadale, W. coast of Skye. Old Red Sandstone Rocks. | At Slade, County Wexford. Carboniferous Limestone Rocks. | At Featherd. County Wexford. On Old Red Sandstone Rocks. | At Tramore, County Waterford. On Silurian slates. |
| I. Sub-Regeo. | Fucus canaliculatus. Littorina rudis. | Fucus canaliculatus. Littorina rudis. | Fucus canaliculatus. Littorina rudis. | Fucus canaliculatus. Littorina rudis. A few Balani. | Fucus canaliculatus. Littorina rudis, and petræa. | Fucus canaliculatus. Littorina rudis. A few Balani and Patellæ. | Fucus canaliculatus. Littorina rudis, petræa, and Balani. |
| II. Sub-Regeo. | | | Lichina. Patella vulgata. Balanus. | Lichina. Patella vulgata. Mytilus edulis. | Lichina. Patella vulgata. Balanus. Nullipora. | Lichina. Patella vulgata. Balanus. Mytilus edulis. Nullipora. | Lichina. Patella vulgata. Balanus. Mytilus edulis. |
| III. Sub-Regeo. | $\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \ \end{matrix}}\right.}$ $\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$ | Fucus articulatus. Balanus. littorina littorea. Purpura lapillus. Fucus nodosus. | Fucus articulatus.Balanus.littorina littorea.Purpura lapillus.Acinea mesembryanthemum.Fucus nodosus, forming a distinct belt. | Fucus articulatus and Fucus nodosus, mingled.Patella vulgata and Balani, abundant.littorina littorea.Purpura lapillus, abundant.Trochus umbilicatus.Spirorbis on rocks.Corallina officinalis. | Fucus articulatus and nodosus, mingled.Balanus.littorina littorea.Purpura lapillus.Trochus crassus.Acinea mesembryanthemum. | Fucus articulatus. Balani, abundant. littorina littorea. Purpura lapillus. Trochus umbilicatus, and crassus. Acinea mesembryanthemum. | Fucus articulatus. Balani and Patellæ littorina littorea. Purpura lapillus. Trochus umbilicatus. Acinea mesembryanthemum. Corallina officinalis. |
| IV. Sub-Regeo. | Fucus serratus, its fronds covered with spirorbis. | Fucus serratus, its fronds covered with spirorbis. | Fucus serratus, its fronds covered with spirorbis.littorina neritoides.Lottia testudinaria. | Fucus serratus, mingled with nodorous.Spirorbis.littorina neritoides.Trochus cinerarius.A few Balani. | Fucus serratus.littorina neritoides.Trochus cinerarius and umbilicatus, with occasional specimens of T. ziziphinus. | Fucus serratus.littorina neritoides.Trochus cinerarius.A few Patellæ and Balani. | Fucus serratus.littorina neritoides. |
| Intermediate bands, only a few inches broad, everywhere. | Himanthalia. | Himanthalia. | Conferva rupestris, forming a belt | Four belts of Fuci.1. Laurencia pinnatifida.2. Conferva rupestris.3. Choadrus crispus.4. Himanthalia lorea. | Chondrus crispus, and Himanthalia lorea. | Himanthalia. | Himanthalia. |
| Region of Laminariæ | Laminariæ. | Laminariæ. | Sand with Zostera. | Laminaria. | Laminaria, and Delesseria. | Laminaria. | Laminaria. |
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. Here we find the great assemblage of carnivorous mollusca, the species of Fusus, Pleurotoma, and Buccinum. and many of the species of Trochus, Here too are most abundant the Naticæ, ,,Fissurellæ, Emarginulæ, Velutinæ, Capulus, Eulimæ, and Chemnitziæ, and among bivalves, Artemis, Venus, Astarte, Pecten, Lima, Arca, and Nucula, Numerous and peculiar Radiata, including the largest and most remarkable species, abound, and, for number, variety, and interest of the forms of animal life in the British Seas, this region transcends all the others. Its vertical range is from 15 to about 50 fathoms; its chief development between 25 and 35 fathoms.
The fourth and lowest of the regions of depth in the British Seas, I have termed the region of deep-sea corals. It is necessarily local as the greater extent of our marine area does not attain the depth at which this region commences, zoologically about 50 fathoms, or possibly considerably deeper. It has as yet been but very partially explored, but so far we know, is well characterized by the abundance of the stronger corals, the presence in quantity of species of the Dentalium-like genus of Annelides, called Ditrupa, by a few peculiar Mollusca, and by peculiar Echinodermata, as Astrophyton and Cidaris, and Amorphozoa, as Tethya cranium. All our British Brachiopoda inhabit this zone, and probably ​range throughout it. Even, in certain localities, where they are found in shallower water inhabiting the region of corallines, there are reasons, as will afterwards be shown, for believing that such cases are apparent anomalies which may be explained by reference to geological changes.
The following table may be useful as exhibiting at a glance the characteristic features of the several zones of depth in the British Seas.
Table of the Regions of Depth of the British Seas.
| | Characteristic Plants. | Characteristic Animals. |
| I. Littoral Zone. The tract between tide marks. | First Subregion. Fucus canaliculatus. Second Subregion. Lichina. Third subregion. Fucus articulatus. Fourth Subregion. Fucus serratus. | Patella vugata throughout. First Subregion. Littorina rudis. Second Subregion. Mytilus edulis. Third subregion. Littorina littorea.Purpura lapillus. Fourth Subregion. Littorina neritoides.Trochi. |
| Himanthalia lorea. |||
| II. Laminarian Zone. Tract between low-water mark and 15 fathoms. | Subregio superior Laminariæ. Rhodomeniæ. Delesseriæ. Subregio inferior Nullipora. | Trochus Ziziphinus. Lacunæ. Patella pellucida. Patella Cærulea. |
| III. Region of Corallines. 10 to 50 fathoms. | ? | Hydroid zoophytes throughout Subregio superior Fucus antiquus. Pullastra virginea. Pecten maximus. Subregio inferior Pleurotoma teres. Turbinolia milletiana. |
| IV. Region of deep Sea Corals. 50 fathoms to beyond 100. | 0 | Subregio superior Neæræ. Celleporæ. Brachiopoda. Ditrupa. Subregio inferior Astrophyton. Cidaris. Oculina. Primnoa. |
We have a right, then, to infer that the associations of testacea observed in the British glacial deposits, present a northern or arctic aspect as compared with our existing marine fauna, not owing to conditions of greater depth prevailing during the epoch of their existence, but owing to a general colder climate affecting the area within which they are found, and due to causes not now in operation within that area. As these beds in Britain probably approached the southernmost bounds in Europe of the true glacial formation, the regions more to the north in which similar beds are found with similar fossils, must have been formed under similar, and, judging from the greater paucity of species of organic remains in them as compared with the numbers in the British beds, probably severer climatal conditions. So far as I have seen, there is no British case of an upheaved stratum of the glacial formation containing organic remains evidently untransported, which may not have been formed at a less depth than 25 fathoms, and as the Nullipora occasionally occurs in the deeper beds—to which belong most of the clays and marls—it is probable that between 10 and 15 fathoms would more frequently approach the truth. Over a great part of the areas occupied by these glacial beds, we find the uppermost portion composed of sand and gravel, containing fossils more ​general, littoral, and indicating a much less depth of water than existed previously during the deposition of the marls. The abundance of Purpura lapillus, and the presence of Littorina littorea, may be mentioned as especially characteristic of the shelly gravels which in Wexford have been found by Captain James to contain numerous specimens of the reversed variety of the Fusus antiquus, known under the name of Fusus contrarius, and common in the red crag. At present the reversed form is as rare among specimens of that Fusus, as the dextral form was anciently. It is difficult to conjecture a sufficient cause for the prevalence of the monstrous over the normal form during two geological epochs. The discovery by Captain James of Turritella incrassata (a crag fossil), of a southern form of Fusus, and of a Mitra, allied to a Spanish species, in these southern Irish beds, associated with the usual glacial species, is an important fact, suggesting the probability of a communication southwards of the glacial sea with a sea inhabited by a fauna more southern in character than that now existing in the neighbourhood of the region where these relics were found. It is a fact which will bear strongly on the question of the point of time, whether before, during, or after the glacial epoch, certain freshwater beds containing important fossils, remains of vertebrata and mollusca, were deposited. It also bears importantly on the general question of the distribution of climates on this side of the Atlantic during the later tertiary periods. At present we have an intermediate (the Celtic) marine fauna, separating the Boreal and South-European or Lusitanian types. But that such an intermediate type need not have existed at a time when the Boreal fauna ranged, almost exclusively, farther south than now, we may convince ourselves by looking to the state of the marine fauna at the opposite coasts of the Atlantic. In latitude 42° N., we find a cape of no great prominence, and of recent geological origin, constituting the barrier, or rather marking the line of demarcation between a fauna of character in great part as northern as that which prevailed in our seas during the glacial period, and one of fully as southern a character (if not more so) as that now prevailing on the coasts of Portugal. For a short space, and but a very short space, the two faunas intermingle; but there is no distinct intermediate marine fauna like that now widely separating the northern and southern European types. The best evidence I can quote on this subject is that of Dr. Gould, whose State Report on the Invertebrata of Massachusetts, is a most carefully elaborated and excellent work. 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. No specimen of Cochlodesma, Montacuta, Cumingia, Corbula, Janthina, Tornatella, Vermetus, Columbella, Cerithium, Pyrula, or Ranella, has yet been found to the north of Cape Cod; while Panopæa, Glycimeris, Terebratula, Cemoria, Trichotropis, Rostellaria, Cancellaria, and probably Cyprina and Cardita, do not seem to have passed to the south of it. Of the 197 marine species (of the Massachusetts fauna), 83 do not pass to the south shore, and 50 are not found on the north shore of the cape. The remaining 64 take a wider range, and are found on both sides." (p. 315). A little farther north and we have the contrast still more evident on each side of Cape Breton, the true boundary southward on the coast line of the Boreal fauna, which north of it ranges on to Greenland, and is probably very nearly the existing representative of the ancient fauna of our seas during the glacial epoch.
The probability of the peculiar fossils noticed as occurring only in the southernmost Irish beds of the glacial epoch, indicating a proximity of the glacial sea with one peopled by mollusks of a Lusitanian type, is supported by the fact that in the newer pliocene beds of southern Italy, we find associated with the characteristic existing mollusca of the Mediterranean certain Red Sea and Indian Ocean species on the one hand, and Celtic species on the other, both now extinct in that region. It is worthy of notice, that the Celtic fossil species found in the Sicilian beds, Mya truncata, Lutraria solsnoides, Cyprina islandica, Ostrea edulis, Patella vulgata, Fusus antiquus contrarius,, and Buccinum undatum, present the association of species characteristic of the southern bounds of glacial beds in Britain; and it can scarcely be doubted that during the newer pliocene epoch, which I regard as synchronic with the glacial period in the north, there was a communication open between the Mediterranean and North Seas on the one hand, by which this influx of Boreal or Celtic forms was acquired, whilst, on the other, there was, or had lately been, a free communication with the Indian Ocean through the Red Sea,—the Isthmus of Suez not existing.
​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. At the present day there are sixty-six species of testaceous mollusks common to the coasts of the United States, north of Cape Cod, and Europe. Of these sixty-six species, not one has its northern European limit south of Britain, and only ten (excluding two pelagic forms) range to the seas of Southern Europe, and of these some are doubtful identifications. On the other hand, no fewer than forty-five are recorded inhabitants of the Arctic Seas,—and probably many more live there, for I have no lists by which to institute a comparison of the British fauna with that of Lapland, or even Iceland. In the following table the first column contains the names of testacea common to Europe and North America, as recorded by American authors of repute, especially Dr. Gould, who took every pains to identify his species correctly with their European analogues. Some few of these are doubtful; and it will be observed, that the doubtful species are just those deficient in the middle column, exhibiting the localities in which the species have been found fossil in beds of the glacial epoch. In the third column the European and Arctic ranges of the species are given, This table shows that no fewer than fifty-one out of the sixty-five are known as glacial fossils. Of the remaining fourteen, two, viz., Spirula Peronii and Janthina fragilis are pelagic mollusks wandering from the south, and with them may be classed Teredo navalis, carried about in floating wood. Two, Kellia rubra and the Skenea, are minute species living in stony ground near highwater-mark, and not likely to be preserved fossils; whilst the three Chitons, although larger from inhabiting similar situations, and being extremely fragile, falling to pieces after death, are in the same category. The Modiola glandula (Crenella decussata of English conchologists) is also a minute shell. Modiola discrepans and discors are doubtful identifications. The remainder, including Buccinum Donovani, and two species of Margarita, may yet be expected to occur in the drift.
From this table we may fairly infer, that the identity, so far as it exists, between the testaceous fauna of Boreal America and that of Europe, was established, at latest, during the glacial epoch; and the occurrence of some American forms in the crag, as we have previously mentioned, would show that it commenced prior to that epoch. It is very important to observe that the ancient relationship between the marine mollusks of the new and old world is not maintained by pelagic species or floaters—the few of those in the list are recent introductions ​
| Mollusca common to the East coasts of North America and Europe (as named by American anthors). | Places where the same species are found fossil in formations of the Glacial Epoch. | Distribution of the species in the Artic and European Seas. |
| Teredo navalis................................................................................................................................................................................................................................................................................................................................................................................................ | ................................................................................................................................................................................................................................................................................................................................................................................................ | General, from Greenland southwards. |
| Pholas crispatus................................................................................................................................................................................................................................................................................................................................................................................................ | Sweden, Britain................................................................................................................................................................................................................................................................................................................................................................................................ | Seas of Northern and Western Europe. |
| Solen ensis................................................................................................................................................................................................................................................................................................................................................................................................ | Ireland................................................................................................................................................................................................................................................................................................................................................................................................ | Scandinavian, Celtic, and South European Seas. |
| Panopæa arctica................................................................................................................................................................................................................................................................................................................................................................................................ | Clyde................................................................................................................................................................................................................................................................................................................................................................................................ | Northern Seas, very rare near Britain. |
| Mya arenaria................................................................................................................................................................................................................................................................................................................................................................................................ | Britain................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland, Scandinavian, and Celtic Seas. |
| Mya truncata and var. β................................................................................................................................................................................................................................................................................................................................................................................................ | Britain, Sweden, Russia, Canada................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland, Scandinavian, and Celtic Seas. (The variety β not now known alive in Europe). |
| Mesodesma Jauresli (Mactra deaurata)................................................................................................................................................................................................................................................................................................................................................................................................ | ................................................................................................................................................................................................................................................................................................................................................................................................ | A doubtful or very rare European species. |
| Tellina groenlandica................................................................................................................................................................................................................................................................................................................................................................................................ | Russia, Canada................................................................................................................................................................................................................................................................................................................................................................................................ | Arctic Seas (Icy Cape). |
| Kellia rubra................................................................................................................................................................................................................................................................................................................................................................................................ | ................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland? Northern, Celtic and Mediterranean Seas. Ranges farther south. Lives at watermark.. |
| Saxicava rugosa................................................................................................................................................................................................................................................................................................................................................................................................ | British, Swedish, Russian beds................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland, and all the European Seas, and as far south as the Canaries. |
| Lucina radula................................................................................................................................................................................................................................................................................................................................................................................................ | Scotland? Sweden?................................................................................................................................................................................................................................................................................................................................................................................................ | Celtic and Mediterranean Seas. |
| Lucina flexuosa................................................................................................................................................................................................................................................................................................................................................................................................ | Scotland................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland; Northern, British, and Mediterranean Seas. |
| Astarte compressa................................................................................................................................................................................................................................................................................................................................................................................................ | Britain................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland, Scandinavian, and British Seas. |
| Astarte danmoniensis (with scotica)................................................................................................................................................................................................................................................................................................................................................................................................ | Britain, Sweden, Russia................................................................................................................................................................................................................................................................................................................................................................................................ | British and Northern Seas. |
| Astarte borealis................................................................................................................................................................................................................................................................................................................................................................................................ | Britain, Sweden, Russia................................................................................................................................................................................................................................................................................................................................................................................................ | Arctic, Norwegian, and Zetland Seas. |
| Cardium groenlandicum................................................................................................................................................................................................................................................................................................................................................................................................ | Russia................................................................................................................................................................................................................................................................................................................................................................................................ | Arctic Seas. |
| Cyprina islandica................................................................................................................................................................................................................................................................................................................................................................................................ | Britain, Denmark................................................................................................................................................................................................................................................................................................................................................................................................ | Northern and British Seas. |
| Nucula (Leda) hyperborea (var. of myalis?)................................................................................................................................................................................................................................................................................................................................................................................................ | Ireland, Sweden, Canada................................................................................................................................................................................................................................................................................................................................................................................................ | Arctic Seas. |
| Nucula (Leda) minuta................................................................................................................................................................................................................................................................................................................................................................................................ | Britain, Russia?................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland, Scandinavian, and British Seas. |
| Nucula tenuis................................................................................................................................................................................................................................................................................................................................................................................................ | Scotland................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland; North British Seas. |
| Mytilus edulis................................................................................................................................................................................................................................................................................................................................................................................................ | Britain, Sweden, Russia, Canada................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland, Northern and Celtic Seas. |
| Modiola vulgaris................................................................................................................................................................................................................................................................................................................................................................................................ | Britain, Sweden................................................................................................................................................................................................................................................................................................................................................................................................ | Scandinavian and Celtic Seas. |
| "Modiola discrepans" (nigra?)................................................................................................................................................................................................................................................................................................................................................................................................ | ................................................................................................................................................................................................................................................................................................................................................................................................ | (If identical), Greenland, Scandinavian, and North British Seas. |
| "Modiola discors" (our discrepans?)................................................................................................................................................................................................................................................................................................................................................................................................ | ................................................................................................................................................................................................................................................................................................................................................................................................ | (If identical), Greenland, Northern, Celtic, and South European Seas. |
| Modiola glandula (Crenella decussata)................................................................................................................................................................................................................................................................................................................................................................................................ | ................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland. North British Seas. |
| Pecten islandicus................................................................................................................................................................................................................................................................................................................................................................................................ | Scotland, Sweden, Russia, Canada................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland, Iceland. |
| Ostrea borealis (a var. of edulis?)................................................................................................................................................................................................................................................................................................................................................................................................ | (edulis) in Scottish beds................................................................................................................................................................................................................................................................................................................................................................................................ | (edulis), Northern, Celtic, and south European Seas. |
| Anomia ephippium................................................................................................................................................................................................................................................................................................................................................................................................ | Scotland, Sweden................................................................................................................................................................................................................................................................................................................................................................................................ | Northern, Celtic, and South European Seas. |
| Anomia aculeata................................................................................................................................................................................................................................................................................................................................................................................................ | Ireland................................................................................................................................................................................................................................................................................................................................................................................................ | Same as the last. |
| Terebratula caput serpentis................................................................................................................................................................................................................................................................................................................................................................................................ | Sweden................................................................................................................................................................................................................................................................................................................................................................................................ | Northern, Celtic, and Mediterranean Seas. |
| Terebratula psittacea................................................................................................................................................................................................................................................................................................................................................................................................ | Britain, Canada................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland, Scandinavian, and north British Seas (Leakey MSS.). |
| Chiton marginatus................................................................................................................................................................................................................................................................................................................................................................................................ | ................................................................................................................................................................................................................................................................................................................................................................................................ | Scandinavian and British Seas. |
| Mollusca common to the East coasts of North America and Europe (as named by American anthors). | Places where the same species are found fossil in formations of the Glacial Epoch. | Places where the same species are found fossil in formations of the Glacial Epoch. | Distribution of the species in the Artic and European Seas. |
| Chiton ruber (?)................................................................................................................................................................................................................................................................................................................................................................................................ | ................................................................................................................................................................................................................................................................................................................................................................................................ | $\scriptstyle {\left.{\begin{matrix}\ \\\\\ \ \end{matrix}}\right\}\,$ | Greenland, Scandinavian, and British Seas. |
| Chiton albus (?)................................................................................................................................................................................................................................................................................................................................................................................................ | ................................................................................................................................................................................................................................................................................................................................................................................................ | $\scriptstyle {\left.{\begin{matrix}\ \\\\\ \ \end{matrix}}\right\}\,$ | Greenland, Scandinavian, and British Seas. |
| Lottia testudinalis................................................................................................................................................................................................................................................................................................................................................................................................ | Sweden................................................................................................................................................................................................................................................................................................................................................................................................ | Sweden................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland, Scandinavian, and North British Seas. |
| Cemoria noachina................................................................................................................................................................................................................................................................................................................................................................................................ | Scotland, Sweden................................................................................................................................................................................................................................................................................................................................................................................................ | Scotland, Sweden................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland, Scandinavian, and Seas north and west of Scotland. |
| Natica clausa................................................................................................................................................................................................................................................................................................................................................................................................ | Scotland, Sweden, Russian, Canadian................................................................................................................................................................................................................................................................................................................................................................................................ | Scotland, Sweden, Russian, Canadian................................................................................................................................................................................................................................................................................................................................................................................................ | Arctic Seas. |
| Janthina fragilis................................................................................................................................................................................................................................................................................................................................................................................................ | ................................................................................................................................................................................................................................................................................................................................................................................................ | ................................................................................................................................................................................................................................................................................................................................................................................................ | Oceanic (Mid-Atlantic). |
| Velutina lævigata................................................................................................................................................................................................................................................................................................................................................................................................ | Scotland................................................................................................................................................................................................................................................................................................................................................................................................ | Scotland................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland, Scandinavian, and British Seas. |
| Velutina sonata (V. undata, Brown)................................................................................................................................................................................................................................................................................................................................................................................................ | Clyde................................................................................................................................................................................................................................................................................................................................................................................................ | Clyde................................................................................................................................................................................................................................................................................................................................................................................................ | Arctic Seas. |
| Sigaretus haliotoideus (=S. perspicuus)................................................................................................................................................................................................................................................................................................................................................................................................ | Sweden................................................................................................................................................................................................................................................................................................................................................................................................ | Sweden................................................................................................................................................................................................................................................................................................................................................................................................ | British, Mediterranean, and Lusitanian Seas. |
| "Skenea serpuloides," (from the description and figure this should be Skenea depressa, and not serpuloides of Montagu, to which it is referred by Dr. Gould)................................................................................................................................................................................................................................................................................................................................................................................................ | ................................................................................................................................................................................................................................................................................................................................................................................................ | ................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland, Scandinavian, and British Seas. |
| Scalaria groenlandiea)................................................................................................................................................................................................................................................................................................................................................................................................ | Sweden................................................................................................................................................................................................................................................................................................................................................................................................ | Sweden................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland. |
| Margarita cinerea (Tr. inflatus? Smith.)................................................................................................................................................................................................................................................................................................................................................................................................ | Scotland, Sweden................................................................................................................................................................................................................................................................................................................................................................................................ | Scotland, Sweden................................................................................................................................................................................................................................................................................................................................................................................................ | Arctic and Norwegian Seas. |
| Margarita undulata................................................................................................................................................................................................................................................................................................................................................................................................ | ................................................................................................................................................................................................................................................................................................................................................................................................ | ................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland (Zetland, var. β?). |
| Margarite arctica (M. vulgaris)................................................................................................................................................................................................................................................................................................................................................................................................ | ................................................................................................................................................................................................................................................................................................................................................................................................ | ................................................................................................................................................................................................................................................................................................................................................................................................ | (M. vulgaris), Greenland, Scandinavian, and north of Britain. |
| Littorina rudis and var. tenebrosa................................................................................................................................................................................................................................................................................................................................................................................................ | Britain, Sweden................................................................................................................................................................................................................................................................................................................................................................................................ | Britain, Sweden................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland, Iceland, Norwegian, and British Seas. |
| Littorina palliata (L. expansa, Brown)................................................................................................................................................................................................................................................................................................................................................................................................ | Scotland................................................................................................................................................................................................................................................................................................................................................................................................ | Scotland................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland and Norway. |
| Lacuna vincta................................................................................................................................................................................................................................................................................................................................................................................................ | Scotland................................................................................................................................................................................................................................................................................................................................................................................................ | Scotland................................................................................................................................................................................................................................................................................................................................................................................................ | Scandinarian and British Seas. |
| Lacuna neritoides (L. Montagui?)................................................................................................................................................................................................................................................................................................................................................................................................ | Ireland................................................................................................................................................................................................................................................................................................................................................................................................ | Ireland................................................................................................................................................................................................................................................................................................................................................................................................ | Norwegian and British Seas. |
| Pleurotoma decussata (P. reticulata. Brown)................................................................................................................................................................................................................................................................................................................................................................................................ | Scotland................................................................................................................................................................................................................................................................................................................................................................................................ | Scotland................................................................................................................................................................................................................................................................................................................................................................................................ | Scottish Seas. |
| Fusus islandicus (F. corneus of British authors)................................................................................................................................................................................................................................................................................................................................................................................................ | Britain, Sweden................................................................................................................................................................................................................................................................................................................................................................................................ | Britain, Sweden................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland, Scandinarian, and British Seas. |
| Fusus Sabini................................................................................................................................................................................................................................................................................................................................................................................................ | Ireland................................................................................................................................................................................................................................................................................................................................................................................................ | Ireland................................................................................................................................................................................................................................................................................................................................................................................................ | Arctic Seas, Zetland. |
| Fusus tornatus (carinatus, Laskey)................................................................................................................................................................................................................................................................................................................................................................................................ | Scotland, Canada, Russia................................................................................................................................................................................................................................................................................................................................................................................................ | Scotland, Canada, Russia................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland, Finmark, and British Seas (very rare). |
| Fusus scalariformis................................................................................................................................................................................................................................................................................................................................................................................................ | Britain, Sweden................................................................................................................................................................................................................................................................................................................................................................................................ | Britain, Sweden................................................................................................................................................................................................................................................................................................................................................................................................ | Arctic Seas. |
| Fusus Bamffius................................................................................................................................................................................................................................................................................................................................................................................................ | Britain................................................................................................................................................................................................................................................................................................................................................................................................ | Britain................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland, Scandinavian, and British Seas. |
| Fusus rufus?................................................................................................................................................................................................................................................................................................................................................................................................ | ................................................................................................................................................................................................................................................................................................................................................................................................ | ................................................................................................................................................................................................................................................................................................................................................................................................ | British Seas. |
| Fusus turricula................................................................................................................................................................................................................................................................................................................................................................................................ | Britain................................................................................................................................................................................................................................................................................................................................................................................................ | Britain................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland, Scandinavian, and Celtic Seas. |
| Fusus muricatus?................................................................................................................................................................................................................................................................................................................................................................................................ | Ireland................................................................................................................................................................................................................................................................................................................................................................................................ | Ireland................................................................................................................................................................................................................................................................................................................................................................................................ | Celtic and Mediterranean Seas. |
| Trichotropis borealis................................................................................................................................................................................................................................................................................................................................................................................................ | Canada................................................................................................................................................................................................................................................................................................................................................................................................ | Canada................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland, Norwegian, and Scottish Seas. |
| Purpura lapillus................................................................................................................................................................................................................................................................................................................................................................................................ | Britain................................................................................................................................................................................................................................................................................................................................................................................................ | Britain................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland, Scandinavian, and Celtic Seas. |
| Buccinum Donovani (B. glaciale of British authors)................................................................................................................................................................................................................................................................................................................................................................................................ | ................................................................................................................................................................................................................................................................................................................................................................................................ | ................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland. Zetland?. |
| Buccinum undatum................................................................................................................................................................................................................................................................................................................................................................................................ | Britain, Sweden, Russia................................................................................................................................................................................................................................................................................................................................................................................................ | Britain, Sweden, Russia................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland, Scandinavian, and Celtic Seas. |
| Buccinum ciliatum (B. Humphreysianum)................................................................................................................................................................................................................................................................................................................................................................................................ | Scotland? Canadian................................................................................................................................................................................................................................................................................................................................................................................................ | Scotland? Canadian................................................................................................................................................................................................................................................................................................................................................................................................ | Greenland, Scandinavian, and Celtic Seas. |
| Spirula Peronii................................................................................................................................................................................................................................................................................................................................................................................................ | ................................................................................................................................................................................................................................................................................................................................................................................................ | ................................................................................................................................................................................................................................................................................................................................................................................................ | Oceanic (Mid-Atlantic). |
It has been already stated that the remains of testacea through a great part of the glacial or drift-beds, are in a fragmentary or rolled state, and are not distributed in horizons (as they would be if the ground on which they lived had been elevated undisturbed), but are often scattered through confused and unstratified masses of mud and sand or gravel. It has also been stated that this is not everywhere the case: that in certain localities we find the organic remains forming well defined horizons, and in such a state of preservation as to indicate that they lived and died on the spots where they are found; and that among these undisturbed localities we find some which, containing littoral fossils in situ, indicate the lines of coast and tide-mark. These facts suggest two questions: 1st, what were the disturbing influences? and, 2nd, how far are we to regard all drift beds containing marine remains as having been formed beneath the sea, on the spots where they now are found?
So far as I have observed the fossils in the great exposed tracts of northern drifts as in Ireland, the north of England, and the Isle of Man, are generally fragmentary or rolled. Occasionally strata occur in the midst of the beds less disturbed than the greater part of them, and containing shells apparently in situ; but through the greater part of the epoch of their deposition, disturbing influences appear to have been at work throughout the area of the glacial sea. These disturbing influences were probably of two kinds—the phoughing-up action of icebergs, and the sweeping action of great waves coming from the north.
To the first may be attributed the general confused condition of the mud bottoms, and the fragmentary and disturbed state of their included fossils, which are all species, not transported, but occurring in undisturbed localities, in such a state as to prove that they were indigenous to the seas in the upheaved beds of which they are now found.
To the second, the transport to very high levels of masses of marine drift with organic remains, may be referred, either by washing up, high and dry, portions of the sea-bed, or by propelling and stranding masses of ice which, in their turn propelled before them the contents mineral and organic of the sea. For the evidence presented by glacial testacea in situ in all tracts of sufficient extent within the area of the British Isles, shows that at no period during their existence was there a very ​deep sea through the upheaved parts of that area, but on the contrary, that very generally it was a shallow sea which then prevailed, one, judging, from the organic remains, not probably beyond 15 fathoms or so deep. This the occurrence of Nullipora in the parts presenting greatest appearances of depth shows, and beds containing deep-sea Arctic species are nowhere exposed. Besides which we have, as has been already shown, distinct evidence of the coast lines of that epoch. Yet fossils, and those too, not littoral species, occur at very high levels, as for instance in Mr. Trimmer's famous case of Moel Trefaen, in North Wales, where beds of gravel and sand containing glacial marine testacea occur at a height of 1,500 feet above the present sea level. These fossils are deposited in the museum of the Geological Society, where I have lately examined them carefully with a view to see whether they indicate an ancient coast line and beach, or an ancient sea-bottom. But they cannot be regarded as indicating either, being a confused mixture of fragments of species from all depths, both littoral and such as invariably live at a depth of many fathoms—of such species as Astarte elliptica, Mytilus edulis, Tellina solidula, Cardium edule, Venus gallina, Buccinum undatum, Mactra solida, Dentalium entalis, Cyprina islandica and Turritella terebra, inhabitants, some of muddy grounds, some of sandy, some of rocky. Deep and shallow water species mingled could at no time have lived together, or have been thrown up on one shore. They indicate the action of some disturbing influence—of having been accumulated far above the level of the then existing sea, through the agency of an iceberg, as suggested by Mr. Darwin, or through the agency of a wave of translation, such as Sir Roderick Murchison has shown to play so important a part in producing the phenomena of the Scandinavian and Russian drifts; or possibly by the combined action of both causes. That such propelling forces derived from afar, were powerful agents of disturbance at the period under consideration, is also rendered probable by the fact that the chief localities of stratified glacial beds, containing undisturbed testacea evidently in situ—as, for instance, great beds of Pecten islandicus, Panopæa arctica, and even such delicate forms as Nuculæ Tellinæ, and Lucinæ in the position in which they lived, and with both valves connected, are to be found in the Clyde districts (where this fact was noted by Mr. Smith) in localities sheltered to the north by mountain ridges which were anciently islands in the glacial sea. These islands had saved many tracts of sea from the disturbing influences of icebergs, and great advancing waves, the course of which, from the north, is indicated by the protected beds; for it is worthy of note that the glacial beds in the northern districts of Scotland, which had no such protecting barriers to defend them—as, for instance, those at Wick—present the same disturbed and unstratified ​conditions, and similar rolled and broken fossils with those so characteristic of most of the glacial beds around the Irish Sea.
The upheaval of the bed of the glacial sea, was not sudden but gradual. The phenomenon, so well described by Professor Forchhammer in his essays on the Danish drift, indicating a conversion of a muddy sea of some depth, into one choked up with sand banks, though not universal, are equally evident in the British Isles, especially in Ireland and the Isle of Man. In the latter locality, the marl beds containing bivalves of the second or third region in depth, are capped by a great thickness of sands and gravels, occasionally containing littoral shells, but rolled. On these sands the larger boulders usually lie. In Ireland Captain James has found the littoral shells in abundance in the sandy beds, especially in such localities as were evidently close upon the ancient coast line. The period of the extinction, as a race, of the reversed variety of Fusus antiquus may be referred to that of the upheaval of the Irish sandy beds.
The close of the glacial epoch, ending in this upheaval of the bed of the glacial sea, marks the commencement of a new era in our fauna, and, as we have already seen, of our flora. As a great part of the area, previously occupied by water, now became land, the banishment of a number of species necessarily took place, many of which, in consequence of the change of conditions arising from the causes of their expulsion, retired for ever. The remodelling of our area, which afterwards took place, the formation of the Irish Sea, of the German Ocean, and of a new line of coasts, events calling new influences into play, introduced the existing population of our seas. Part of our glacial testacea had been extinguished, part retired to more congenial arctic seas, and a few disappeared from the coasts of Europe, while they continued inhabitants of the shores of America. A considerable number, however, returned to the seas of their ancestors, where they became and remain the associates of numerous forms, some newly called into being to people the new-formed seas, some coming with favouring currents from the warmer seas of the south. Among the latter were a number of forms which had not always been strangers to the British Seas. During the genial times preceding the glacial epoch, more than fifty species of testacea, inhabitants at present of our seas, lived in them whilst the crag beds were in process of formation but disappeared under the chilly influences of the sub-arctic epoch which succeeded. As either a re-creation (a notion inconsistent with the line of argument I have adopted in this essay) of these forms must have taken place, or else a re-migration of them from some distant point where they had lived on, amid favouring conditions, when banished from the British Seas,—an inquiry ​whettier they may be traced in formations syn-chronic with the glacial beds, is of no little interest and geological importance.
Whilst eocene, miocene, and older pliocene marine beds,—represented in our own country by the London clay, and the coralline and red crags,—are found in many parts of the north and middle of Europe and America, the "newer pliocene," such as is typified by the Sicilian tertiaries, those of Rhodes and other parts of the Mediterranean basin, is nowhere present within the area of the marine glacial beds, which, on the other hand, are nowhere to be met with within the area of the marine tertiaries of the Sicilian type. The latter, however (as we have already seen), includes a number of characteristic glacial forms which no longer exist in the same marine provinces, but are restricted to the northern or Celtic Seas. It is, therefore, extremely probable—I may say certain—that the glacial formations are "newer pliocene," and the SicUian tertiaries contemporaneous with the northern drift. As the sea in which those tertiaries were deposited communicated with the glacial seas, we might expect, à priori, to find among the relics of that ancient Mediterranean the still-surviving species which had lived in our seas previously to the glacial period, but had retired during its continuance.
The following table will shew that our search has not been in vain:—
Table of British existing Testacea which inhabited our area before the Glacial Epochs but during it had retired to other seas.
| Species. | Formations of Older Date than Northern Drift in which they occur in Britain. | Foreign Newer Pliocene beds in which they occur. |
| Gastrochæna pholadia. | Coralline crag. | Sicily. |
| Thracia pubescens. | Coralline crag. | Sicily. |
| Lepton aquamosura? | Coralline crag. | |
| Pandora margaritacea. | Coralline crag. | |
| Montecuta 8ubstriata. | Coralline crag. | |
| Montecuta ovata. | Coralline crag. | |
| Kellia suborbicularis. | Coralline crag. | Sicily. |
| Lucina rotundata. | Coralline and red crags. | Sicily. |
| Tellina donacina. | Coralline crag. | S. Italy, Archipelago. |
| Psammobia vespartina. | Coralline crag. | Sicily, Archipelago. |
| Psammobia scopula. | Coralline crag. | Sicily. |
| Psammobia florida. | Coralline crag. | S. Italy. |
| Cytherea chione. | Coralline crag. | Sicily, Archipelago. |
| Venerupis irus. | Red crag. | Sicily, Archipelago. |
| Pullastra Virgines. | Red crag. | Sicily. |
| Venus ovata. | Coralline and red crags. | S. Italy, Archipelago. |
| Isocardia cor. | Coralline and red crags. | S. Italy, Archipelago. |
| Cardium nodosum. | Coralline and red crags. | |
| Arca noæ. | Coralline and red crags. | S. Italy, Archipelago. |
| Arca raridentata. | Coralline crag. | S. Italy. |
| Modiola discora. | Coralline crag. | Sicily. |
| Pinna ingens? | Coralline and red crags. | |
| Lima fragilis. | Coralline and red crags. | Sicily, Archipelago. |
| Lima subauriculata. | Coralline crag. | Sicily. |
| Pecten tumidus. | Coralline crag. | Sicily. |
Table of British existing Testacea which inhabited our area before the Glacial Epochs but during it had retired to other seas.
| Species. | Formations of Older Date than Northern Drift in which they occur in Britain. | Foreign Newer Pliocene beds in which they occur. |
| Emarginula Fissura. | Coralline and red crags. | Sicily. |
| Adeorbis subcarinatus. | Coralline crag. | Sicily. |
| Scissurella crispate. | Coralline crag. | |
| Trochus conulus. | Coralline crag. | A. Italy, Archipelago. |
| Trochus Montecuti. | Coralline crag. | |
| Rissoa zetlandica. | Coralline crag. | |
| Rissoa reticulata. | Coralline crag. | S. Italy. |
| Rissoa striata. | Coralline crag. | |
| Rissoa vitrea. | Coralline crag. | |
| Eulima polita. | Coralline and red crags. | Sicily, Archipelago. |
| Eulima subulata. | Coralline crag. | Sicily. |
| Scalaria clathatulus. | Coralline crag. | Archipelago. |
| Chemnitzia elegantissima. | Coralline crag. | Sicily. |
| Odostomia plicata. | Coralline crag. | Sicily. |
| Tornatella tornatilis. | Coralline and red crags. | Sicily. |
| Cerithium tuberculatum. | Coralline crag. | |
| Cerithium adversum. | Coralline crag. | Sicily. |
| Pleorotoma lineare. | Coralline and red crags. | Sicily. |
| Bulla catenata. | Coralline crag. | Sicily. |
| Bulla lignaria. | Coralline and red crags. | Sicily, Archipelago. |
| Bulla cylindracea. | Coralline and red crags. | |
| Bulla truncata. | Coralline crag. | Sicily. |
| Chiton fascicularis. | Coralline crag. | Sicily. |
Thus closely are we enabled to track the course of the forms which disappeared for a time from our seas and then returned. A knowledge of the geology of Spain and Portugal, as yet but very partially explored, may show hereafter that their place of refuge was not so far distant as the region into which we have followed them. The currents from the south sweeping the Lusitanian shores, and impinging over our own coasts—as Rennell's current for example—were, probably, and are still, powerful agents in the diffusion of the species, and in bringing about the present mixed condition of our marine fauna. In like manner, currents from the north probably brought back some of the sub-arctic forms so characteristic of the drift. But at certain spots within our area we find assemblages of northern forms so peculiar and so isolated, boreal patches, as it were, that we cannot account for them by any facts connected with the present disposition of the currents, or other transporting influence. These "patches" are especially to be met with in the Clyde district, and among the Hebrides, where they have been explored by Mr. MacAndrew; they have also been observed by Captain Otter, R. N., of Her Majesty's surveying ship Sparrow, on the east coast in the Murray Firth. It is probable there is a similar patch somewhere near the Nymph Bank on the east coast of Ireland, and another in the German Ocean. They have, usually, for their centre, a hole or valley of considerable depth, from 80 to beyond 100 fathoms. Their inhabitants are decidedly of more northern character than the members of the ​Celtic fauna, and the species are such as are assembled together far to the north on the coast of Norway. Among them are many of the most remarkable of the forms, found fossil, in the glacial beds, as Cemoria noachina, Trichotropis borealis, Natica groenlandica, Astarte elliptica, Nucula pygmæa. These are associated with Terebratula caput serpentis, Crania norvegica, Emarginula crassa, Lottia fulva, Pecten danicus, Neæra cuspidata, costata and abbreviata, and many peculiar echinoderms and zoophytes, which are either species known only far north, or found only at considerable depths in localities farther to the south.
As these northern "outliers"—a term which well expresses their character—occur in districts which are remarkable for the number and extent they present of upheaved glacial sea-bottoms, their depth and contents have suggested the following explanation:—
When the bed of the glacial sea was upheaved, that upheaval, as we have already seen, raised above water only such portions of it as had been formed in a moderate depth. Such tracts of that sea as were of moderate depth, and consequently inhabited by a peculiar fauna, would still remain below water, though changed in level. A portion of their fauna,—whose organization might be too delicate to endure the sudden change of conditions,—would be destroyed; but another portion, consisting of such species as had greater capacities for vertical range, would survive; for in the deeper parts of the seas of our area, conditions of temperature would still remain such as were required by these isolated northern forms. Let a, of the following diagrams, represent the conformation of a part of the British Seas during the Glacial epoch, throughout their area, of which a boreal or subarctic fauna prevailed; at the close of that epoch the elevation of the sea-bed, whilst it converted into dry land its shallower portions, left the deeper tracts (which within our area were few in number and small in extent) still under water (diagram b). In these depths the arctic forms would still live on, whilst climatal changes would so alter the zoological character of the shallows of our seas (as represented in the unshaded portions of water in figure b), as to isolate the assemblages of animals in the depths, and leave them, as it were, in the condition of northern outliers.
This isolation of the northern marine animals, and restriction of them ​to the depths of our seas, is exactly comparable to the change in our flora, brought about by the same geological events. During the Glacial epoch, the group of islands now forming the mountains of Britain, were doubtless clothed with a vegetation correspondent in character to the northern and Scandinavian assemblage of marine animals which then inhabited the surrounding sea (diagram c). The origin of this flora has been inquired into in the earlier part of this essay. The subsequent change of level converted these islands into mountain summits, on which the original flora was preserved and isolated (diagram d), whilst new and warmer climatal conditions introduced over the middle and low ground a vegetation of a more temperate character to become the general flora of the new-formed land.
I have already shown that in the law of representation by plants of latitudes by zones of elevation, the element of representation has been confounded with that of identity. If this be true in the vertical distribution of terrestrial creatures, it should also be true with respect to that of marine, which I have elsewhere shown obey a similar law in their vertical distribution, representing parallels of latitude by zones of depth. This I have demonstrated in the case of the Ægean mollusca.
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. One, a minute species of Rissoa, was new; and had been previously taken by Mr. MacAndrew in the British Seas, but only at great depths. The remaining four were Nucula nuclea (a northern variety), Nucula tenuis, Leda minuta, and Lima subauriculata. Of these the number of examples of Nucula tenuis and Leda minuta exceeded greatly those of their companions; they are both essentially northern and Arctic forms, ranging ​from Greenland to the Scottish Seas, and not known south of Britain. The Nucula nuclea and the Lima range from Greenland to the Mediterranean, but the variety of the former taken is confined to northern seas, and the latter is very rare, and only found at great depths in seas south of Britain. The dead mollusks taken were Abra Boysii, a species of similar range with Nucula nuclea, Cardium Lövenii a Scandinavian species, and Pecten danicus, a Norwegian species, found only in the British Seas in the lochs of the Clyde, and there rarely alive, though dead valves are abundant, as if the species thus isolated were now dying out. The echinoderms were Ophiocoma filiformis, and Brissus lyrifer, the former a Norwegian species; the latter ranging to the Arctic Seas, but southwards not known beyond the Clyde region. The Crustacean was new, both as to genus and species. It will be observed, that the assemblage of animals thus taken at this great depth, was essentially Arctic, Subsequently we added to the list three species of Neæra, N. costellata, N. rostrata, and N. abbreviata. Of these the second ranges throughout the European Seas. All three are known inhabitants of the Mediterranean, where they are found associated only at very great depths. All three are inhabitants of the coasts of Norway, where they have been observed by Professor Löven.
Deep dredgings elsewhere on the British coasts yielded similar results, the assemblages of deep-sea species presenting a decidedly boreal character, and maintaining the representation of the faunas of northern latitudes, mainly through identical species.
In the deepest of the regions of depth in the Ægean, this representation of a northern fauna is maintained, partly by identical and partly by representative forms. The three species of Neæra, already mentioned, the Pandora obtusa, the Arca pectunculoides, the Saxicava rugosa, Pecten similis, Trochus millegranus, Fusus echinatus, Rissoa reticulata, and Terebratula cranium, are instances of the former, whilst Crania ringens, Abra profundissima, Astarte pusilla, Cardium minimum, Nucula sulcata and ægeensis, Leda commutata, Lottia unicolor, and Pleurotoma abyssicola are examples of the latter. The presence of the latter is essentially due to the law [of representation of parallels of latitude by zones of depth], whilst that of the former species depended on their transmission from their parent seas during a former epoch, and subsequent isolation. That epoch was doubtless the Newer Pliocene, or Glacial Æra, when the Mya truncata, and other northern forms, now extinct in the Mediterranean, and found fossil in the Sicilian tertiaries, ranged into that sea. The changes which there destroyed the shallow-water glacial forms, did not affect those living in the depths, and which still survive.
​In the preceding observations on the marine zoological phenomena, presented by the drift, I have strictly confined myself to evidence derived from beds of the same age, and universally recognised as typically belonging to the "northern drift," properly so called, i.e., formations of the Glacial epoch. There are, however, two English formations containing marine shells, many of them characteristic glacial species, the synchronism of which, with the glacial beds of the north-east of England, of Scotland, and Ireland, has not been granted, or has been received with a doubt These are the beds at Bridlington and the marine parts of the mammaliferous crag.
The discovery in the Irish drift of several of the most characteristic testacea of the mammaliferous crag, not elsewhere observed in glacial beds, has thrown a new light on the nature of both the English deposits of doubtful age, and enables us, without much misgiving, to refer them to the glacial epoch, and to regard them as probably marking its commencement before the severer climatal conditions had set in. We have seen already that m the red crag certain boreal species appear. In the mammaliferous crag the number of these increases, and the number of the southern forms materially decreases. The following analysis of the valuable catalogue of mammaliferous crag shells, included in the lists of Mr. Searles Wood, will show the state of our testaceous fauna on the eastern province of the British region during the period when that formation was deposited.
They consist, 1st, of species now living in the British Seas, and found fossil in true glacial beds. Those marked with an asterisk are elsewhere in contemporaneous beds, either confined to, or chiefly found in, the Irish drift.
​2. Of living British species usually regarded as Northern, but not observed hitherto in glacial beds.
3. Of living British species not found fossil in typical glacial beds, but occurring in contemporaneous Italian newer pliocene strata.
4. Of species not now known in the British Seas, but still living in the Mediterranean. Not fossil in drift beds elsewhere.
Cardita corbis.
5. Of glacial species of Arctic origin; with the exception of the first, not now living in, or doubtful inhabitants of, the British Seas.
Terebratula caput serpentis,
Scalaria groenlandica var. similis,
Tellina calcarea (vars. obliqua, prætenuis and ovata).
Nucula oblongoides (hyperbarea).
6. Of extinct crag forms, those marked with an asterisk, are new species of Mr. Wood.
From the beds at Bridlington, Mr. Lyell enumerates 35 species of testacea, of which 20 were living forms, and 26 species common to the mammaliferous or Norwich crag. I have had an opportunity of examining a collection from this locality belonging to my friend Mr. Bowerbank, who, with his accustomed liberality, has permitted me to make use of it. It includes 28 species. Of these, Dentalium entalis, Aporrhais pespelicani, Littorina littorea, Turritella terebra, Buccinum undatum, Anomia ephippium?, Saxicava rugosa, Astarte compressa, Tellina solidula, Pleurotoma turricula, and Balanus balanoides, are common living British species known also as fossils in most glacial beds.
Trichotropis borealis, Natica groenlandica, Fusus Sabini and Astarte borealis, are rare North British species of Arctic origin.
Fusus fornicatus and scalariformis, Tellina groenlandica, are Arctic and Boreal American species, the first extremely rare, the others not now living in the British Seas.
​Cancellaria costellifer is a species, found fossil in the red crag, not now known living in the European Seas, but still surviving on the coasts of North America.
These are accompanied by Nucula Cobboldiæ, and by Cardita scalaris, a crag species now extinct, and probably representative of the existing Cardita arctica. With them are a species of Astarte and a Natica, both new to me.
The examination of the Bridlington fossils has convinced me that they are truly of the age of the mammaliferous crag, and that both those formations may be referred to the epoch of the Northern Drift, and probably—especially the last mentioned—to the commencement of that epoch before the severer conditions had set in. This view is borne out by the presence of Cyrena trigonalis and Paludina unicolor (freshwater mollusks still surviving in southern regions) in freshwater beds containing mammals which do not appear after the drift along with mollusks which are common living British species now. These freshwater formations (as that of Gray's in Essex) are probably contemporaneous in part with the marine strata of the red crag. If, as I am informed by Mr. Trimmer, the Norwich crag marine beds of Bramerton alternate with freshwater beds, local phenomena of elevation and depression are indicated during the commencement of the Glacial epoch, which would account for the disappearance of some of the peculiar forms in the Norwich crag, whilst the extinction of Nucala Cobboldiæ, the Cancellaria and the Cardita, all local species, was evidently due to the conversion of the area of the crag seas into sand.
Immediately after the elevation of the bed of the great glacial sea, a great part of the area now occupied by the Celtic province of the European Seas must have been in the condition of dry land, forming extensive plains. The state of the existing fauna of the German Ocean, as compared with the fauna of that portion of our area during the Crag epochs and the commencement of the Glacial epoch, proves that the change was such as to destroy the ancient population of that sea,—doubtless through the conversion, probably gradual, of its bed into land. How far northwards this land extended it is now impossible to say, but we find the fragments of it bordering the seaside, even to the farthest parts of the mainland of Scotland. It linked Britain with Germany, Iceland, and Denmark; and a corresponding plain united Ireland with England. When considering the distribution of our flora, we derived our Germanic plants and animals from the mainland of Europe, across this ancient land. Whether the breaking up of it was slow or rapid, it ​is impossible to determine, but judging from the effect of the sea in destroying the portions which remain, we may suppose that it was rapidly effected in some places, and at certain times.
That the climatal conditions of the area thus converted from sea into land, were not suddenly but gradually altered, is shown by fair evidence. In the beautiful volume on the history of our Fossil Mammalia and Birds, by Professor Owen, we have an immense mass of invaluable information on the distribution "of our ancient land-animals brought together. If we select from this treasury of palæontological knowledge the portions which concern the area and epoch under discussion, and lay down on our map the ranges of those of our quadrupeds which distinctly inhabited Britain after the Glacial epoch,—and in this category I would include most of the cave-animals,—we shall see distinct indications of climatal conditions prevailing over a great portion of that area very different from those now existing. The position of the remains of the Cervus megaceros in basins of freshwater marls, containing existing testacea, resting in depressions of the upheaved glacial sea-bed (as in Ireland and the Isle of Man), gives a clue to the prevailing condition during the earliest post-glacial times. We cannot suppose that the limited tract of drift forming the northern extremity of the Isle of Man, in which there are numerous freshwater basins, containing entire skeletons of the Megaceros, was other than portion of a larger region inhabited by that remarkable deer. Now these basins are distinctly, both in the Isle of Man and Ireland, overlaid by the peat, with its ancient included forests.
[Diagram showing the relations of the freshwater marls (b) to the glacial marine beds (a), and overlying peat with included forests (c), in the Isle of Man (d), represents the old slates.]
The epoch of the Megaceros was anterior to the epoch of the Forests which aided in the formation of the great peat bogs, so frequently resting on the northern drift. This, too, was probably the time when the reindeer ranged in our country nearly to the 52° parallel. Also the beaver and the Bos primigenius, both of which survived their companions, and lived on for a time during the succeeding age of great forests. The Bos longifrons, the Cervus elaphus, the Elaphus primigenius, the horse, the wolf, and probably the bear, ranged over a great part of the British area during the intermediate time, and had become generally distributed before the breaking-up of the great central plain, occupying the position of the existing Irish Sea. When the land became covered ​by forests, a portion of Britain became included within the ranges of the hyenas, tigers, rhinoceros, aurochs, and their numerous associates, some now altogether extinct, some still existing, though not found in Britain, and some yet numbered among our indigenous quadrupeds.
To this epoch may be referred such an association of extinct mammalia, with freshwater shells, all at present existing, observed by Professor Phillips in Yorkshire.
Many of these animals probably inhabited some portions of the area under review; especially the south-eastern and western parts during the epoch of the Red Crag, and at the commencement of the Glacial epoch, contemporaneously with the associations of existing and extinct or southern forms of freshwater mollusca met with in the freshwater lake deposits of Essex, and the neighbouring counties, and equivalent in part to the marine formations of the mammaliferous crag. As the climate became severer, such species may have retired, and on a favourable change of conditions have again returned to their ancient haunts, —just as we have found the testacea to have done in the neighbouring seas, under the same circumstances. Thus in England, even as Mr. Lyell has observed in the case of the mastodon in America, we have the same species of Elphas, Rhinoceros, Felis, Canis, Equus, and other genera, both before and after the drift, in the former cases accompanying species (as the Mastodon angustidens, and the Cyrena), which were never to reappear; in the latter being present during their last days, as it were, at the first birth and in-coming of creatures destined to take their places. The same probably happened with the plants. Mr. Trimmer assures me of the existence of ancient forests of oak and pine distinctly below the drift, yet equivalent to the mammaliferous crag beds. Mr. Lyell quotes the authority of Mr. Robert Brown, for the existence of the spruce (Pinus abies) in similar ancient forests on the coast of Norfolk. The latter tree no longer ranges to our islands. It has retired to the far north.
We have seen that a parallel with the conditions of the fauna of the European Seas during the Glacial epoch is now to be met with on the coasts of Boreal America—that on the eastern shores of the New World between the 40th and 60th parallels of north latitude a Boreal fauna, corresponding to that of the Scandinavian and Arctic Seas of Europe meets, without an intervening assemblage of animals comparable with that of our Celtic province, a fauna equivalent to that of the southern European Seas. The point of meeting in America marks the point of cessation of the influence of the cold currents from the Arctic Seas on the one hand and that of the warm gulf-stream on the other. It corresponds to a similar state of things in the vegetation of the neighbouring mainlands, for it indicates the northern limits of the fourth botanical ​ region of Professor Schouw (that of Solidagos and Asters), equivalent to the great Mediterranean flora (the third province, that of Labiatæ and Caryophylliæ, in Schouw's arrangement)—and the southern bound of the characteristic flora of Labrador, which is equivalent to that of Northern Scandinavia; there being no intermediate flora equivalent to the Germanic in Europe. It indicates, in like manner, the point of meeting of two great zoological regions, the one northern, the American province of fur-bearing animals, the European equivalent of which must be sought in the north of Scandinavia—the other southern and characterized through a great part of its extent by the presence of the opossum (Didelphus virginiana), and the racoon (Procyon lotor); there being no intermediate mammalian province comparable with that of which the wild cat and the mole are typical in Europe. The distribution of the great marine mammals corresponds; the region of habitual haunt of whales, of the range of the walrus, Phoca leporina and Phoca groenlandica, corresponding in the American Seas to the extension southwards of the Boreal American zoological and botanical land provinces and extending many degrees south of the ranges of the same animals in the European Seas. It is remarkable that the southern limit of the occasional range of whales in the European Seas, corresponds to that of the newer pliocene deposits containing Arctic fossils—doubtless their ancient habitual range.
The great Boreal American land province is a tract including the Canadas, Labrador, Rupert's Land and the countries northwards. It equals Europe in extent. Its zoological features have been investigated by Sir John Richardson, its botanical by Mr. Robert Brown and Sir William Hooker. Both zoologically and botanically it is divisible into two great regions. The northern, known to the hunters as the "barren grounds," is a treeless tract extending from Hudson's Bay in the 60th parallel of north latitude to the great Bear Lake in the 65th. It corresponds to the American division of Schouw's first botanical province. The southern division is wooded (Pinus microcarpus and Pinus Banksiana are characteristic trees) and embraces many degrees of latitude presenting a surprising uniformity every where in its ferine inhabitants.
​Among the animal population of the barren grounds we find north of the 70th degree the reindeer, the musk ox, a wolf, the Arctic fox, the white bear, the Arctic hare and the ermine and the shrew. Between 60° and 70° most of these animals live associated with the brown bear. The Canadian otter, the American hare, the zibet, Felis canadensis, the elk and the Bos americanus, most of which are abundant in the wooded region and accompanied there with other species of Cervus, Lepus, Meles, Vulpes, Ursus, Felis and Lutra.
It seems to me that we have in these two divisions of the great Boreal American province a parallel to the successive epochs of the fauna of Britain after the upheaval of the bed of the glacial seas—a first when our country was in the condition of the barren grounds, bare and treeless, when the reindeer, the Irish elk, the Bos primigenius, lived along with species of bear, fox, wolf, hare, cat and beaver—the assemblage of animals found in the freshwater marl basins below peat; a second when forests of pine, oak and beach overspread the land, and forest-living animals, tree-browsing herbivora, prowling and lurking carnivora, and most, if not all, of our existing indigenous mammals became the population of Britain. The change from the first condition into the second was in all probability gradual and marked by the gradual extinction or retirement of species adapted for the colder, and the introduction of such as were fitted for the more temperate epochs.
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. Their parent region appears to have been Siberia. There they abounded during the last tertiary epoch. Thence they migrated westwards when the regions of the glacial ocean were converted into land. The climatal and geographical conditions which induced their diffusion were but the harbingers of others which led to their destruction. They retired probably to their original specific centres and perished in the land of their origin. From their associates we can judge of their habits, and there can scarcely be a doubt that the ancient elephants and rhinoceroses of Britain and the associated extinct quadrupeds were creatures adapted to severer climatal conditions than those now prevailing in our area, and not like the existing forms of the genera to which they belonged, members of faunas more southern than our own. Probably the existing zoological features of Northern and Central Asia present the truest ​analogy with the latest zoological conditioiis of the west of Europe, including Britain, during the epoch preceding that by common consent of geologists termed historical.
Connected with the latest changes included in the historical period are the phenomena of raised beaches, properly so called, distinguished by Mr. Smith from the true glacial beds and containing numerous testacea all characteristic species and similarly associated with those now living in the British Seas; and the raised estuary and beach-beds described by Sir Henry De la Beche in the Report on the Geology of Devon and Cornwall. In that work there is described a most interesting section observed by Mr. Henwood at the Carnon Stream Works, where we find sand with sea shells covering the remains of a forest, containing bones of the red deer and human skulls, which rests in turn on tin ground considered by Sir Henry as equivalent to the rhinoceros gravels of Lyme Regis. On the subject of the evidences of the latest changes of level on our southern coasts the essays of Mr. Austen in the Geological Transactions are full of valuable observations.
The agency of man has both added to and diminished the number of our plants and animals. The epochs of the destruction of the wolf and of the beaver are historical events, whilst other more useful creatures have been introduced and naturalized. Even among the invertebrata we find man involuntarily adding to and diminishing the number of our resident species. Now, the draining of lakes destroys the rarer freshwater mollusks, whilst the formation of canals diffuses new forms—as in the case of Dreissena polymorpha—all over the country. The progress of cultivation drives before it, and finally banishes, many an indigenous but useful flower, and at the same time introduces others as useless, and perhaps not so harmless, to take its place. With the good comes the evil, and the hand that sows the corn diffuses the dodder. Fortunately the records of natural history have been begun in good time, and the influence of man's agency through the progress of civilization, and. its accompaniments, is of too recent action to affect the statistics of our science.
Great as the changes appear to be affecting the disposition of land and water, during recent geological periods, as compared with the present, assumed by me in this essay, I cannot but express my conviction that future research will not only confirm these, but prove that still greater took place during the epochs under inquiry. 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. Although I have made ice-bergs and ice-floes the chief agents in the transportation of an Arctic flora southwards, I cannot but think that so complete a transmission of that flora as we find in the Scottish mountains, was aided perhaps mainly by land to the north, now submerged. It is difficult otherwise, too, to account for the cessation of the Arctic littoral mollusks in the Scottish glacial beds, and their replacement by other forms in the English and Irish beds of the same epoch. When dredging on the great fishing-banks bounding the Zetland Isles, and forming long ridges, now in fifty and more fathoms below the sea, stretching from some unexplored point in the north, like long arms, down to the Scottish shores, and covered with angular fragments of the rocks of which they are formed, I was strongly struck with their resemblance to the rugged and broken surfaces of the neighbouring islands, and could not divest myself of the notion that these banks were submerged mountain chains. Before, however, this can be fairly assumed, we must have a re-examination of the vegetable and animal productions of Iceland, that great northern centre of volcanic power, the presence of which where it is, is possibly intimately connected with the phenomena we have been endeavouring to interpret.
The chief conclusions to which the facts and arguments stated in this essay lead, may be summed up as follows:—
1. The flora and fauna, terrestrial and marine, of the British Islands and Seas, have originated, so far as that area is concerned, since the meiocene epoch.
2. The assemblages of animals and plants composing that fauna and flora, did not appear in the area they now inhabit simultaneously, but at several distinct points in time.
3. Both the fauna and flora of the British Isles and Seas are composed partly of species, which, either permanently or for a time, appeared in that area before the Glacial epoch, partly of such as inhabited it during that epoch, and in great part of those which did not appear there until afterwards, and whose appearance on the earth was coeval with the elevation of the bed of the glacial sea, and the consequent climatal changes.
4. The greater part of the terrestrial animals and flowering plants now inhabiting the British Islands are members of specific centres beyond their area, and have migrated to it over continuous land before, during, or after the Glacial epoch.
5. The climatal conditions of the area under discussion, and north, east, and west of it, were severer during the Glacial epoch, when a great ​part of the space now occupied by the British Isles was under water, than they are now or were before, but there is good reason to believe, that so far from those conditions haying continued severe or having gradually diminished in severity southwards of Britain, the cold region of the Glacial epoch, came directly into contact with a region of more southern and thermal character than that in which the most southern beds of glacial drift are now to be met with.
6. This state of things did not materially differ from that now existing under corresponding latitudes in the North American, Atlantic, and Arctic Seas, and on their bounding shores.
7. 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.
8. The floras of the islands of the Atlantic region, between the Gulfweed bank and the Old World, are fragments of the great Mediterranean flora, anciently diffused over a land constituted out of the up-heaved and never-again submerged bed of the (shallow) Meiocene Sea. This great flora, in the epoch anterior to, and probably, in part, during the ​Glacial period had a greater extension northwards than it now presents.
9. The termination of the Glacial epoch in Europe was marked by a recession of an Arctic fauna and flora northwards, and of a fauna and flora of the Mediterranean type southwards, and in the interspace thus produced, there appeared on land the general Germanic fauna and flora, and in the sea that fauna termed Celtic.
10. The causes which thus preceded the appearance of a new assemblage of organised beings, were the destruction of many species of animals and probably also of plants, either forms of extremely local distribution, or such as were not capable of enduring many changes of conditions—species, in short, with very limited capacity for horizontal or vertical diffusion.
11. All the changes before, during, and after the Glacial epoch, appear to have been gradual and not sudden, so that no marked line of demarcation can be drawn between the creatures inhabiting the same element and the same locality, during two proximate periods.
​12. The relationship now existing between the faunas and floras of Boreal America and Europe, both marine and freshwater, was established during (probably towards the close of) the Glacial epoch.
13. 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.
Throughout this essay I have used the epithet "glacial," in connexion with the words "epoch," "beds," and "formation," in a sense which purists in geological phraseology may consider objectionable. 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. I have selected the word "glacial," in order to remind the geologists of the ice-charged condition of our seas during that epoch,—conditions which probably did not prevail during its earlier stage, and the gradual disappearance of which marked its conclusion. As, however, it appears almost certain that the "Glacial epoch," and that of the deposition of Sicilian and Rhodian tertiaries were synchronic it would be advisable to adopt some term to express that geological period as a whole, and by which to designate the formations of that period. Mr. Lyell's term, "pleistocene," would, perhaps, best serve the purpose, as that of "newer pleiocene" is not sufficiently distinctive, and may lead to confusion. In this case, among English tertiaries, the coraline crag would rank as meiocene, the red crag as pleiocene, the glacial beds as pleistocene, and the megaceros freshwater marls and marine raised beaches as two stages of post-tertiary.
The line of argument I have adopted is equally applicable to the investigation of the relations, geological and palæontological, of the ancient geological epochs, one with another, as of the present with the geological past. If the constancy of species, and the mutual relationship through a common descent, of all the individuals composing each, be granted, this diffusion in time and space will, when traced, furnish us with a new clue to the determination of the configuration of land and water, during the epochs when they existed, and also to the extension or limitation of peculiar climatal conditions, during each period, and to the causes which replaced them by others.
EXPLANATION OF THE DIAGRAMS.
I.—Diagram of the distribution of British Phanerogamous Plants and Marine Mollusca.
In this diagram the Roman numerals within circles indicate the terrestrial provinces in which we find the several sub-floras composing the British flora chiefly developed, and the arrows with coloured flukes indicate the directions they took in their migration from the continent. I. is the region of the west Irish flora, or Asturian type. II. is the region of the Devon flora, or Norman type. III. is the region of the Kentish flora, or the north French type. IV. is the region of the Alpine flora, or Scandinavian type. V. is the sign of the great Germanic or central European type, which must be understood as mingled up in the other regions—overspreading, as it were, the country. The orange tint represents I.; the pink, II.; the yellow, III.; the blue, IV., and the green, V.
The marine molluscan faunas are indicated by Roman numerals, not surrounded by circles, and by arrows with barred tails; the number of the bars on the tail of an arrow indicates the number of the type, the direction of which, in the course of its migration, is marked by the direction of the arrow, and the turning point by curved arrows. The types which are nonmigratory are indicated by numerals only, and those which are universally distributed over the area represented in the map are omitted.
Diagram II.
In this map I have endeavoured to convey a graphic idea of certain geological, zoological, and botanical features presented by the region of the north Atlantic, either now or at former epochs, and which throw light on the history of the Pleistocene formations, and of our existing fauna and flora.
The space coloured blue represents the portion of the northern hemisphere anciently, and in part at present, under the condition of which a glacial or boreal fauna, is characteristic. The dark blue represents such a region as now existing; the pale and dark together indicate the ancient glacial region. Throughout this region an uniform assemblage of marine testacea lived during the glacial epoch. Two-thirds of the same species now live assembled together in the region coloured dark blue, including all the forms of northern origin now extinct in the European portion of the pale-blue area. The bound of the dark-blue region indicates the line within which ice floated in summer, and which is constantly inhabited by the larger cetacea. The bound of the pale-blue region agrees very nearly with the limit of the occasional range of whales now.
​At the southern bound of the dark-blue region a molluscanfauna, equivalent to the Lusitanian on the European side of the Atlantic, meets with one of a Boreal character. A similar feature is presented by the drift fossils of the pale-blue region at the point of meeting with the yellow, on the European side.
It is to be observed, that within the blue region all pleistocene fossiliferous beds contain fossils of the glacial type; and that south of it within the yellow the fossils of the equivalent beds are of the Sicilian newer pleiocene type.
The purple lines and bounds mark spots and provinces wherein we now find a flora, or the fragments of a flora, of an Arctic or truly Boreal character. It will be observed that in Europe this flora is indicated as fragmentary, and marks the lines of mountain chains, whilst in the new world (within the dark-blue line) it indicates constant Boreal regions of vegetation.
The yellow marks a region, the greater part of which was probably continuous land between the close of the meiocene epoch and the commencement of the pleistocene. The Gulf-weed bank, repeating the form of the meiocene coasts of the Old World, indicates its Atlantic bounds. Over this region I suppose the Asturian flora to have migrated to Ireland, and afterwards (during the Glacial epoch) to have been isolated, and in great part destroyed. This was a region of shallow sea during the Meiocene epoch, bounded by a gulf of deep water, dividing the marine zoological provinces of the old world from those of the new.
The lines of colour mark the regions of existing floras.
1st. The purple, already mentioned, marks the region of Arctic and Boreal floras.
2nd. The orange encircles the region of the Mediterranean flora, and includes the fragments of the ancient post-meiocene land. During such a condition of things as prevailed during the Glacial epoch (judging from the present state of the opposite side of the Atlantic), the orange line then extended farther north, and approached the purple, then circumscribing most of the land within the blue region.
3rd. The green bounds the region of the existing Germanic flora, and includes the space elevated at the close of the Glacial epoch, when the orange and purple lines receded from each other. The extension of this land included Iceland, where we now find a considerable assemblage of Germanic plants isolated.
APPENDIX.
CATALOGUE OF SPECIES OF MARINE ANIMALS,
The remains of which are found Fossil in Beds of the Glacial Epoch.
[In the following catalogue I have endeavoured to rectify the nomenclature of the species. The principal synonyms are given; the chief localities in which the species are found fossil in formations of the Glacial epoch; their distribution at present in the sea; and a concise geological history of each, so far as the British area is concerned.]
VERTEBRATA.
Mammalia.
The following Cetacea, probably belonging to beds of this epoch are enumerated by Professor Owen:—
Phoæna crassidens. Monodon monoceros. Physæter macrocephalus. Balænoptera boops. Balæna mysticetus.
Pisces.
Mallotus villosus.
Locality, fossil. Canada (Mr. Logan).
Loc., living, Greenland.
Mollusca.
Brachiopoda.
1. Terebratula psittacea. (Anomia sp.), Linnæus.
Loc., fossil. Ayrshire. Bramerton. (Canada.)
Loc., living. Seas of Newfoundland, Labrador, Greenland, and Norway. It is inserted in British lists, on doubtful authority. In a copy in my pos- session of the "Catalogue of North British Testacea," by Captain Laskey, interleaved and enriched with manuscript notes in the author's handwriting, is the following memorandum:—"Terebratula psittacea, Turton. The under valve was found by me on the shore of Aberlady Bay, at low water, and since, a perfect specimen by dredging in the deeps of the Frith of Forth. 20th July, 1825."
2. Terebratula caput serpentis.
Syn., T. aurita, Fleming, T. costata. Lowe.
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.
Note. The great horizontal and vertical range of this species corresponds with its range in time. The Terebratula striatula of geologists—a species which commences its range in the upper green sand, and is found in the upper and lower chalk, and in the London clay—appears to be identical with it. Hence it may be regarded as one of the oldest of existing animals.
Order Palliobranchiata.
3. Pholas crispata, Linnæus.
Loc., fossil. In a fragmentary state in the drift beds of Ireland. With the valves united and in situ at Bridlington. In the mammaliferous crag at Postwick, near Norwich. [Sweden.]
Loc., living. In the northern and Celtic regions of the European Seas, and on the coasts of Boreal America and the United States, as far south as Carolina (De Kay). A member of the littoral zone.
Note, An inhabitant of the British Sea, during the epochs of the Red and Coralline Crags.
4. Solen siliqua, Linnæus.
Loc., fossil. In the Clyde beds, the Irish drift, and the mammaliferous crag at Bramerton.
Loc., living. In all the European Seas. Littoral.
Note, Appeared in the British Seas during the epoch of the Red Crag.
5. Solen ensis, Linnæus.
Loc., fossil. In the Irish and Lancashire drift.
Loc., living. Throughout the European Seas, and on the coast of Boreal America. Littoral.
Note, Fossil in the Belgian Crag, according to Nyst.
6. Panopæa arctica (Glycimeris sp.), Lamarck.
Syn., P. Aldrovandi of British authors. P. Bivonæ of Phillippi, and of Mr. Smith's catalogue. P. norvegica of the mineral conchology. P. Spengleri of Valenciennes.
7. Mya truncata, Linnæus.
Loc., fossil. Frequent in the clays and sands of the British drift, occurs in situ, with united valves in the Clyde district. The short variety (var. Uddevallensis) is found in the Clyde beds. Both varieties are found in the glacial formations of Scandinavia, Russia, and Canada.
Loc., living. In the Celtic and northern seas of Europe, the seas of Greenland and of Boreal America, as far south as Cape Cod. The short variety is now found living in the Gulf of St. Lawrence (Captain Bayfield), but ​is not known on the European shores. The range of Mya truncata in depth is much beyond that of Mya arenaria. It inhabits the littoral, laminarian and coralline zones on the coasts of Britain.
Note, Mya truncata appeared in the British Seas during the epoch of the Coralline Crag, and has inhabited their area ever since. During the Glacial epoch it extended its range to the Mediterranean region, where it is now extinct. Sphenia Swainsoni is the young of Mya ovalis, of Turton, the half-grown shell.
Loc., fossil. In situ with both valves united in the Clyde beds.
Loc., recent. Very rare in the British Seas. More frequent in the Arctic Seas of Europe, and those of Boreal America.
Note. Appeared in the British Seas during the epoch of the Red Crag. During the Glacial epoch it extended its range to the Mediterranean region, where it is now found fossil in the Sicilian tertiaries.
8. Mya arenaria, Linnæus.
Loc., fossil. Generally distributed through the British glacial beds. In the mammaliferous crag at Bramerton. [Sweden, Canada].
Loc., recent. The seas of northern and Celtic Europe; of Greenland and of the coasts of Boreal America, as far south as New York.
Note. Appears in the British during the epoch of the Red Crag. It is found fossil in the Campinian beds of Belgium, according to M. Nyst.
9. Mya lata, Sowerby.
Loc., fossil. In the mammaliferous crag of Bramerton.
Note. It is found among the red crag fossils, but it is not known living.
10. Mactra stultorum, Linnæus.
Syn., Mactra magna, Woodward.
Loc., fossil. Mammaliferous crag at Thorp.
Loc., living. Generally distributed through the European Seas, and according to Phillippi, it inhabits the Red Sea.
Note. Appeared in our own area during the Red Crag epoch.
11. Mactra solida, Linnæus.
Syn., Mactra dubia and M. ovalis, Sowerby.
Loc., fossil. General in the sands and clays of the drift. Mammaliferous crag of Thorpe.
Loc., living. All the European Seas.
Note. Occurs in both red and coralline crags; also in the Campinian beds of Belgium.
Mactra striata of Mr. Smith (Wern. Trans., vol. viii. pl. 1. f. 22) appears to be a variety of this.
12. Mactra truncata, Montagu.
Loc., fossil. In the Forth beds (of the Glacial epoch?).
Loc., living. The British Seas.
13. Mactra subtruncata, Montagu.
Syn., Mactra cuneata, Woodward.
Loc., fossil. In the mammaliferous crag at Thorpe. In the Forth beds.
Loc., living. In the British and Northern Seas.
Note. Appears in the red crag.
​14. Mactra arcuata, Sowerby.
Loc., fossil. In the mammaliferous crag.
Note. Not known living. Appeared in the British Seas during the Coralline Crag epoch, and lived through that of the Red Crag.
15. Lutraria elliptica, Lamarck.
Syn., Mactra lutraria, Linnæus. Lutraria vulgaris, Fleming.
Loc., fossil. In the Irish and Lancashire beds.
Loc., living. In the Celtic and Southern regions of the European Sea.
Note. It is found fossil anterior to the Glacial epoch in both coralline and red crag, and in the Campinian beds of Belgium.
16. Scrobicularia piperata (Mactra sp.), Gmelin.
Mactra Listeri and piperata, Gmelin.
Syn., Mactra compressa, Montagu. Lutraria compressa and piperata, Lamarck. Tellina plana, Donovan. Lutraria Listeri, S. Wood. Amphidesma compressum, Fleming.
Loc., fossil. In the mammaliferous crag at Bramerton.
Loc., living. Throughout the European Seas.
Note. Appeared in our area during the Red Crag epoch.
17. Thracia declivis (Mya sp.), Pennant.
Syn., Anatina convexa, Turton. Amphidesma convexum, Fleming.
Loc., fossil. In clay beds at Belfast in situ.
Loc., living. The British Seas.
18. Abra alba (Mactra sp.), Wood.
Syn., Ligula Boysii, Montagu. Amphidesma album, Fleming. Erycina Renieri, Bronn.
Loc., fossil. Clyde beds, Dalmuir. Mammaliferous crag at Bulcham.
Loc., living. Throughout the European Seas, inhabiting the second and third zones of depth.
Note. Commences its range in the coralline crag.
19. Abra prismatica. (Ligula sp,), Montagu.
Loc., fossil. Greenock (Mr. Smith).
Loc., living. Throughout the European Seas, but chiefly in the north.
Note. Mr. Searles Wood records it as a fossil of the coralline crag.
20. Abra intermedia, W. Thompson.
Syn., Amphidesma obovale, S, Wood.
Loc., fossil. Mammaliferous crag of Southwold.
Loc., living. North and west of Ireland, and coast of Scotland. Denmark.
Note. Appears first in the red crag.
21. Montacuta bidentata (Mya, sp.), Montagu.
Loc., fossil. A Bridlington fossil, in Mr. Bowerbank's collection, appears to belong to this species.
Loc., living. European Seas (and coasts of Boreal America ?).
22. Corbula nucleus, Lamarck.
Syn., Corbula striata, Fleming. Mya inæquivalvis, Montagu. Corbula rotundata, Sowerby (Min. Conch.).
​Loc., fossil, Scottish and Irish glacial beds. In the mammaliferous crag at Bramerton.
Loc., living. Throughout the European Seas.
Note. Fossil in the coralline and red crags.
23. Saxicava rugosa (Mytilus sp.), Linnæus.
Syn., Hiatella rugosa, Fleming. Saxicava pholadis of Lamarck; Solen minutus of Linnæus; Hiatella oblonga of Turton; Hiatella arctica of Lamarck, and Mytilus præcisus of Montagu, are all varieties of this protean species. Agina purpurea of Turton appears to me to be a form of the young shell.
Loc., fossil. One of the most generally distributed shells in the glacial beds. It occurs in all the Irish, Scotch, and English fossiliferous drifts and glacial clays, including the Bridlington beds and the mammaliferous crag of Thorpe. Abroad it is found in the glacial formations of Scandinavia, Russia, and Canada.
Loc., living. In all the seas of Northern and Arctic Europe, Boreal America, and Greenland. It ranges as far south as the Canary Isles, (d'Orbigny). Its vertical range is very great. In the British Seas it is found abundantly in the laminarian and coralline regions. In the Mediterranean I have observed it alive at all depths between twenty and eighty fathoms.
Note. Saxicava rugosa appears in all its forms in the coralline, and afterwards in the red crag.
24. Saxicava sulcata, Smith.
Loc., fossil. In the Clyde, Swedish, and Canadian beds.
Loc., living. Is not this the Greenland Mga byssifera of Otho Fabricius? It is possibly only a variety of the last.
25. Psammobia feroensis (Tellina sp.), Gmelin.
Loc., fossil. In the Lancashire and Irish drift. Always rare.
Loc., living. In the beds of Northern and Celtic Europe, frequent Rare in the Mediterranean.
Note. Occurs in the coralline crags; also in the Campinian beds of Belgium, according to M. Nyst.
26. Donax trunculus, Linnæus.
Loc., fossil. In the Irish beds. In the mammaliferoua crag at Bramerton.
Loc., living. Throughout the Celtic and South European Seas, ranging to Senegal (Adamson). Phillippi mentions it among the Red Sea shells collected by Von Hemprich and Ehrenberg. It is always littoral.
Note. The earliest appearance of Donax trunculus in the British area dates from the epoch of the Mammaliferous Crag, It is among the species marked by Phillippi as very rare in the Sicilian tertiaries.
27. Tellina crassa. Gmelin.
Syn., Tellina obtusa, Sowerby (Min. Conch.). Arcopagia crassa, Browm
Loc., fossil. Mammaliferous crag at Portwick. Some fragments from the Irish beds appear to belong to this species.
​Loc., living. The Celtic Seas.
Note. Fossil in both coralline and red crag. It inhabited the Mediterranean region during the Glacial epoch, and is found fossil in the Sicilian tertiaries, but no longer exists so far south.
28. Tellina tenuis, Pennant.
Loc., fossil. In the Scotch beds.
Loc., living. Throughout the European Seas. Always littoral, or nearly so.
Note. Appears to date its origin from the Glacial epoch.
29. Tellina bathica, Linnæus.
Syn., Tellina solidula of British authors.
Loc., fossil, Dalmuir. Frequent in the Irish and western English beds; 'Isle of Man, Bridlington, mammaliferous crag of Bramerton. [In the 'Scandinavian beds.]
Loc., living. Throughout the European Seas. In the Black Sea (Krynicki).
Note. First appeared during the Glacial epoch.
30. Tellina groenlandica, Beck.
Loc., fossil. Bute. (Russia, Canada.)
Loc., living. Arctic Seas, Icy Cape. Gulf of St. Lawrence (Captain Bayfield).
31. Tellina calcarea, Gmelin.
Syn. T. proxima, Brown. T. ovalis, Woodward. T. ovata and obliqua of the Mineral Conchology, and T. prætenuis of Woodward appear to me to be varieties of this species.
Loc., fossil. Clyde beds. The varieties in the mammaliferous crag at Bramerton and Portwick. [Sweden, Russia, Canada.]
Loc., living. In the Arctic Seas [Deshayes]. Behring's Straits [G. B., Sowerby]. Greenland [Möller].
Note. T obliqua, begins in the coralline, the other varieties in the red crag.
32. Tellina fabula, Gmelin.
Loc., fossil. Maimmaliferous crag of Southwold.
Loc., living. Throughout the European Seas.
33. Lucina flexuosa (Tellina sp.), Montagu.
Syn. Venus sinuosa, Donovan. Lucina sinuosa, Lamarck. Cryptodon flexuosum, Turton. Ptychina biplicata, Phillippi.
Loc., fossil, Clyde beds (in situ).
Loc., living. Abundant in the seas of Northern Europe. British Seas. Rare in the Mediterranean. Greenland. Seas of Boreal America.
Note. The Mediterranean variety differs slightly from that found in the Atlantic, and resembles the form fossil in the coralline crag. Nyst includes in this species the "Axinus angulatus," of the Mineral Conchology, a London-clay fossil, which is certainly distinct, though nearly allied. Two fossils were figured in the Mineral Conchology as species of the genus Axinus—the Axinus obscurus (Min. Conch., t. 314), a magnesian limestone fossil, and the eocene Lucina of the subgenus Cryptodon, figured as Axinus angu​latus (Min. Conch., t. 315). Mr. King, of Newcastle, has constituted a genus under the name of Schizodus for the former, but as the latter belongs to a known genus, and the former was the type of the Sowerbian genus Axinus, that name cannot be superseded by Schizodus.
34. Lucina radula (Tellina sp.), Montagu.
Syn., Venus borealis, Pennant. Venus spuria, Dillwyn. Lucina antiquata, Sowerby (M. C).
Loc., fossil. Ireland? In the mammaliferous crag at Thorpe [Sweden].
Loc., living. In the Scandinavian and British Seas (frequent). Bare in the Mediterranean [Phillippi]. Coasts of Boreal America [Gould].
Note. Appears in the British Seas during the epoch of the Coralline Crag. Continued during the Bed Crag epoch. In the Campinian beds of Belgium [Nyst]. Common in the Mediterranean region during the Newer Pliocene epoch.
35. Lucina undularia (Loripes sp,), Searles Wood (MSS.).
Loc., fossil. Mammaliferous crag of Bramerton.
36. Lucina astartea, Nyst.
Syn., Lucina gyrata, Searles Wood (MSS.).
Loc., fossil. Mammaliferous crag of Bramerton.
Note. In the crag of Belgium.
37. Astarte borealis (Venus sp.), linnæus.
Syn., Astarte plana, Sowerby (M. C). Crassina Withami, Smith and Brown.
Loc., fossil. Frequent in the glacial beds of Scotland, Ireland, and the north of England. Bridlington. Mammaliferous crag of Bramerton. [Sweden, Russia.]
Loc., living. In the Arctic Seas and on the coast of Boreal America. A single fresh valve was dredged by Mr. Mac Andrew and myself in 80 fathoms water, 40 miles to the west of the mainland of Zetland (August, 1845).
Note. Not known in British formations anterior to the Glacial epoch.
38. Astarte elliptica, Brown.
Syn., This shell is usually known as Astarte gairensis, a MS. name given to it by Mr. Nicol, who first observed the species. It is also the Crassina ovata of Brown, which is the more common variety. The Crssina depressaof Brown appears to be a third form. [Astarte sulcata of Nilson.]
Loc., fossil. Every where in the glacial beds of Scotland, Ireland, Wales, and the north of England. [Sweden, Russia.]
Loc., living. Scottish and Northern Seas. Very abundant in the lochs of the Clyde district.
39. Astarte danmoniensis (Venus sp.), Montagu.
Syn., Crassina danmoniensis, Lamarck. Crassina sulcata, Turton, not of Montagu?) Astarte scotica is the young of this species, or a variety in which the margin of the valves is not crenulated. Some conchologists, however, regard the Astarte elliptica as the true A. scotica of Montagu.
Loc., fossil. In the Clyde district, the Isle of Man, Ireland, and the north of England, Bridlington. [Russia.]
​Loc., living. Throughout the Celtic and Northern Seas.
40. Astarte sp.?
Loc., fossil. There is a species in the Bridlington beds, resembling the var. Scotica of danmoniensis, but with more numerous ribs, which I regard as distinct. Is this a smooth-margined variety of the shell which Professor Macgillivray describes from the coast of Aberdeen, and refers to Astarte sulcata of Montagu?—History of Molluscous Animals of Aberdeen, &c., p. 259.
41. Astarte compressa (Venus sp.), Montagu.
Syn. Astarte angulata, Woodward. Venus Montagui, Donovan. Cyprina compressa, Turton. Astarte multicostata, Macgillivray (non Smith). Crassina convexiuscula, Brown.
Var. β (latior). Crassina multicostata, Smith. Astarte compressa, Macgillivray.
Loc., fossil. Frequent in all the glacial formations. Bridlington. Mammaliferous crag of Thorpe. [Sweden, Russia.]
Loc., living. Throughout the Northern and Celtic Seas. Seas of Boreal America. The var. β is now especially northern, and in the fossil state is the most abundant form.
Note. Astarte compressa appeared in the coralline crag sea.
42. Astarte pisiformis, Searles Wood.
Syn., Astarte trigonella, Nyst?
Loc., fossil. An undescribed species found in the mammaliferous crag of Bramerton, and in the two preceding crag formations. "Astarte pisiformis is probably A. trigonella of Nyst, pl. 6, f. 18, though his species is not crenulated. It may be a young state, or, what is as probable, a sexual difference." Mr. Searles Wood (in lit.).
[43. Astarte laurentiana, Lyell.
Described and figured in Mr. Lyell's 'Travels in North America,' vol. ii. p. 160. From the glacial beds of Canada].
44. Cyprina islandica (Venus sp.), Linnæus.
Syn. Cyprina maxima, Searles Wood. Cyprina vulgaris, George Sowerby. The identity of this species with Cyprina æqualis of the Mineral Conchology has lately been disputed by Professor Agassiz. Extreme specimens of each are certainly easily distinguishable. Mr. Searles Wood, however, regards them as one species, and no naturalist has had such opportunities of forming a correct opinion. In a note to his 'Catalogue of Shells from the Crag,' in the sixth volume of the 'Annals of Natural History,' he remarks:—"The umbo of this (Cyprina islandica), from the coralline crag, is a little more produced, and appears to have been a thicker shell than the recent, which is the only difference I can detect, while the specimens from the red crag preserve a sort of intermediate character in that respect" M. Nyst also regards Cyprina æqualis as a variety of C. islandica.
Loc., fossil. Common in the British glacial deposits. In the mammaliferous crag of Southwold. [Denmark.]
​Loc., living. In the Northern and Celtic Seas, and Seas of Boreal America.
Note. During the Glacial epoch the range of this well known mollusk extended to the Mediterranean region, where it is found fossil in the newer pliocene beds of Sicily (Phillippi).
45. Cardita scalaris (Venericardia sp.), Sowerby.
Loc., fossil. Bridlington beds.
Note. This species lived during both the preceding crag epochs. The existence of a species of Cardita in the ancient glacial seas of Europe, is paralleled by the presence of a species of the same genus (Cardita arctica) in the seas of Boreal America at the present day.
46. Cardita corbis, Phillippi.
Loc., fossil. In the mammaliferous crag of Southwold (identified by Mr. Searles Wood). In the Campinian beds of Belgium, according to M. Nyst, and present in both coralline and red crag British formations).
Loc., living. The Mediterranean Sea.
47. Artemis exoleta (Venus sp.), Linnæus.
Syn. Cytherea exoleta, Lamarck.
Loc., fossil. In the glacial beds of Scotland, Ireland, Isle of Man, and north of England.
Loc., living. General in the European Seas. Ranges as far south as Senegal (Adamson), is found in the Red Sea, according to Phillippi.
48. Artemis lincta (Venus sp.), Pulteney.
Loc., fossil. Dalmuir (Mr. Smith.)
Loc., living. Celtic and Northern Seas of Europe. The Mediteranean (and Red Sea?) forms belong to Artemis lupinus (Cytherea sp.) of Lamarck.
Is not the Artemis Phillippii of Agassiz ('Iconographie des Coquilles Tertiaires'), also the last-named species?
Note. Artemis lincta is enumerated as a Bordeaux fossil by Basterot; but Professor Agassiz maintains that the Bordeaux form is distinct, and names it A. Basterotii.
49. Venus (Pullastra) decussata, Linnæus.
Loc., fossil. Scotch and Irish beds.
Loc., living. Celtic and South-European Seas. A Red Sea shell according to Philippi.
Note. Not known fossil before the Newer Pliocene epoch. Its probable specific centre was then, as now, in the Lusitanian Seas.
50. Venus (Pullastra) pullastra, "Wood.
Syn., Venerupis pullastra, Fleming. Pullastra vulgaris, G Sowerby.
Loc., fossil. Clyde beds.
Loc., living. Celtic and Scandinavian Seas.
51. Venus (Pullastra) aurea, Linnæus.
Loc., fossil. Near Dublin.
Loc., living. Celtic and South-European Seas.
Note. Neither of the two preceding species are known in beds of older date than the Newer Pliocene epoch.
​52. Venus (Dosina) fasciata, Montagu.
Syn., Venus Brogniartii, Payraudeau.
Loc., fossil. Ireland. Mammaliferous crag of Bramerton.
Loc., living. Celtic and South-European Seas.
Note. Appeared in the British Seas during the Coralline Crag epoch, and has continued ever since. It is now, as anciently, chiefly developed in the Celtic region, from part of which it appears to have been banished during the Glacial epoch.
53. Venus (Pullastra) virginea, Linnæus.
Loc., fossil. Scotland and Ireland.
Loc., living. Throughout the European Seas, but most plentiful in the Celtic region.
Note. Occurs in the red crag.
54. Venus ovata, Pennant.
Syn., Venus pectinula, Lamarck. Venus radiata, Brocchi.
Loc., fossil. Irish and Scotch beds.
Loc., living. Throughout the European Seas, but chiefly abundant in the Celtic and Northern regions. In the Mediterranean it is found for the most part at great depths.
Note. Appeared in our area during the Coralline Crag epoch, and never departed.
55. Venus verrucosa, Linnæus.
Loc., fossil. Among Captain James's Wexford specimens are worn fragments of a Venus, probably of this species; though it would be difficult to distinguish them from similar portions of the crag Venus turgida, or the American Venus mercenaria.
Loc., living. In the southern part of the Celtic region, and throughout the Lusitanian and Mediterranean provinces, where its true centre seems to be. Philippi enumerates it among Ehrenberg and Hemprich's Red Sea shells. Mr. Webb procured it at the Canaries.
Note. It is not known as a British fossil before the Glacial epoch.
56. Venus gallina, Linnæus.
Loc., fossil. In the Irish, English, and Scotch beds, especially in such as indicate their having been deposited as sand in shallow water.
Loc., living. Throughout the European Seas. In the Black Sea, and, it is said, in the Caspian.
Note. Not known fossil in Britain before the Glacial epoch.
57. Venus casina, Linnæus.
Syn., Venus reflexa (young shell).
Loc., fossil Common in the Manx beds, and also found in Ireland and North of England.
Loc., living. Abundant in the Celtic Seas, especially toward the North. Inhabits the South-European Seas, but is very rare, and probably found its way into the Mediterranean during the Glacial or Newer Pliocene epoch, in the sea beds of which it is frequently found fossil. I have found it abundantly ​in newer pliocene tertiaries in the Archipelago, where I never dredged a single living or fresh specimen.
Note. It is not known in either of the ancient crags.
58. Cardium edule, Linnæus.
Syn., C. obliquum, Woodward.
Loc., fossil. General in the Scotch, English, and Irish glacial beds. Mammaliferous crag of Bramerton. (Sweden, Denmark, Russia.)
Loc., living. General through the European Atlantic, and in the Mediterranean, Black and Caspian Seas. It is not known either in Greenland or Boreal America, being replaced there by Cardium islandicum. Its southernmost recorded habitat is the Canary Islands.
Note. Its first appearance in the British Seas was during the epoch of the Red Crag.
59. [Cardium islandicum, Chemnitz.
Syn., Cardium ciliatum, Otho Fabricius.
Loc., fossil. Glacial deposits of Russia and Canada.
Loc., living. Arctic and Boreal American Seas].
60. [Cardium groenlandicum, Chemnitz.
Syn., Venus islandica, of Otho Fabricius, in the Fauna Groenlandica: not of other authors.
Loc., fossil. Glacial deposits of Russia and Canada.
Loc., living. Arctic and Boreal American Seas.
Note. During the Red Crag epoch this species existed in the British Seas.]
61. Cardium exiguum, Gmelin.
Syn., Cardium pygmæum, Donovan.
Loc., fossil. Stated in Mr. Smith's list to be common in newer pliocene deposits. I have not met with it.
Loc., living. The British Seas, and the seas of Southern Europe.
62. Cardium echinatum, Linnæus.
Loc., fossil. Scotish and Irish glacial beds. Isle of Man. [Sicily.]
Loc., living. General in the seas of Europe.
63. Cardium lævigatum, Linnæus.
Loc., fossil. Scotland. Isle of Man, Ireland. [Found in the newer pliocene of Sicily.]
Loc., living. General throughout the European Seas.
64. Pectunculus pilosus (Arca sp.), Linnæus.
Syn., Pectunculus variabilis. Sowerby (M. C.)
Loc., fossil. Isle of Man and Ireland. Mammaliferous crag at Thorpe.
Loc., living. General in the European Seas.
65. Nucula nucleus (Arca sp.), Linnæus.
Syn., Nucula margaritacea, Lamarck.
Loc., fossil. In most of the British glacial beds, but not common.
Loc., living. Throughout the European Seas. Does not range to Greenland.
Note. It occurs in both coralline and red crags.
​66. Nucula proxima, Gould?
Loc., fossil. Among the drift fossils collected by Captain James, in Wexford, is a Nucula, which comes nearer to the above species of Gould, as figured in the 'Invertebrata of Massachusetts' (fig. 63), than to any species with which I am acquainted. The Nucula nitida of Sowerby may, as suggested by Dr. Gould, be the same species; but, if I am right as to the form usually so called, it is only a variety of N. nucleus.
Loc., recent. Seas of Massachusetts. If a deep-sea British form, taken by Mr. W. Thompson in the North of Ireland, and by Mr. MacAndrew on the West of Scotland, be identical, this will add another to the list of species common to Europe and America.
67. Nucula tenuis. (Arca sp.), Montagu.
Syn., Nucula tenera, S. Wood.
Loc., fossil. In the Clyde beds, and in Ireland. In the mammaliferous crag of South Wold.
Loc., living. In the British (chiefly North) Scandinavian and Arctic Seas. Seas of Greenland and Boreal America.
Note. Appears in the red crag.
68. Nucula Cobboldiæ, Sowerby (M. C).
Loc.., fossil. In the mammaliferous crag of Bramerton. Bridlington. A fragment found by Captain James in the Wexford beds probably belongs to this species. It is not now known living. It appeared within our area during the Red Crag epoch, and was probably extinguished by the upheaval of the limited area through which it ranged. It is the finest species of its genus.
Leda. This genus was established by Schumacher for the reception of the beaked Nuculæ. It has been lately revived, and more precisely defined by P. C. Möller, in his 'Index Molluscorum Groenlandiæ.' In that treatise the author groups the forms of Nuculæ inhabiting Greenland under three genera, Leda, Nucula, and Yoldia. Of the first, the Nucula minuta is an example; of the second, Nucula nucleus; and of the third, Nucula arctica. The shell of the first is beaked, and very inæquilateral ; of the second, longitudinally ovate, oblique, and inæquilateral; and of the third, transversely oblong, and usually nearly æquilateral. The essential characters of the animals are enumerated as follows:—
Leda. "Animal tubis, brevibus, tenuibus, rectis præditum; pede longo, tenui, flexili; pallio toto aperto, marginibus simplicibus."
Nucula. "Animal sine tubis exsertilibus, pede brevi, crasso; pallii parte solum inferiore aperta."
Yoldia. "Animal tubis longis curvatis instructum; pede magno, valido; pallio toto aperto, marginibus posticè ciliatis."
I have never seen the animal of a Yoldia; but, having compared those of Nucula and Leda, and the latter with the description given by Möller of Yoldia, I am inclined to restrict the division of the genus Nucula into two generic groups instead of three, and to unite Yoldia with Leda, under the latter name. The animal of Leda minuta, as will be seen by the following sketch, ​has two siphonal tubes, which are long, and may be curved. The margin of the mantle also is crenate.
The animal of Leda pygmæa, which Möller mistook for a true Nucula, and described under the name of Nucula lenticula, is intermediate in character between his Leda and Yoldia, as will be seen from the accompanying figure, drawn from a living Scottish specimen.
In both forms we see exsertile siphons, which are wanting in the true Nuculæ; as in Nucula tenuis.
This important distinction shows that the division of the lamellibranchiated Acephala into two groups, according to the presence or absence of prolonged siphons (corresponding to the integrity or sinuation of the pallial impression in the shell), is artificial. In the Nuculidæ it is evident that the dental characters of the hinge are of more importance. The genus Solenella, which M. A. D'Orbigny has separated from the Nuculidæ, By on account of its sinuated pallial impressions, and placed among the Anatinæ, may therefore be restored to its former and natural position.
69. Leda minuta (Arca sp.), Otho Fabricius.
Syn., Nucula rostrata, Sowerby. Nucula tenuisulcata, Couthouy (fide Gould).
Loc., fossil. In most of the British glacial beds, but not so common as the next (Russia?).
Loc., living. British, Scandinavian, and Arctic Seas. Greenland and Boreal America.
​Note. In the red crag of Sutton.
70. Leda rostrata (Nucula sp.), Lamarck.
Syn., Nucula oblonga, Brown.
Loc., fossil. One of the most characteristic shells of the glacial beds, and very generally distributed. [Sweden, Russia.]
Loc., living. In the Arctic Seas.
71. Leda pygmæa (Nucula sp.), Goldfuss.
Syn., Nucula gibbosa, Smith. Nucula tenuis, Phillippi. Nucula lenticula. Möller.
Loc., fossil. In the Clyde beds, evidently in situ. [In the newer pliocene of Sicily.]
Loc., living. Seas of Greenland. Known only in one spot in the British Seas, viz., the Sound of Skye.
Note. Appeared in our seas during the Coralline Crag epoch, between which time and the Glacial epoch it must have been very generally distributed through the European area.
72. Leda (Yoldia) oblongoides, Wood.
Syn., Yoldia angularis, Möller. Variety of Nucula myalis, Couthouy? Nucula hyperborea, Löven? Bramerton.
Loc., fossil. Found by Captain James in the Wexford beds. [Sweden, Canada.]
Loc., living. In the Arctic Sees.
Note. In the red crag (oblongoides); according to Mr. Searles Wood.
73. Leda. sp. nov.?
The fragment of a species resembling in form the Nucula pusio of Phillippi, ('Enumeratio Moll. Sic.,' vol. ii. to xv. J. S.), but having a smooth exterior, has been found by Captain James in the drift beds of Wexford, where we may expect more perfect specimens of both this and the last.
74. Mytilus edulis, Linnæus.
Syn., M. alæformis, Sowerby (M. C), antiquorum, Woodward.
Loc., fossil. In most of the glacial beds of Britain. Mammaliferous crag at Norwich. [Scandinavia, Russia, Canada.]
Loc., living. Seas of Northern and Celtic Europe; Greenland; coasts of Boreal America. [M. borealis, De Kay.]
Note. Fossil in the red crag.
75. Mytilus (Modiolus) vulgaris, Fleming.
Syn. Modiola modiolus and Mytilus modiolus of many authors, but (according to Mr. Hanley) not the Mytilus modiolus of Linnæus. M. papuanus of Lamarck?
Loc., fossil. Scottish and Irish beds. Mammaliferous crag of Portwick.
Loc., living. British and Scandinavian Seas. Coasts of Boreal America.
76. Pecten islandicus (Ostrea sp.), Muller.
Syn., Ostrea cinnabarina, Born. Pecten Pealii, Conrad (fide Gould).
Loc., fossil. Clyde beds, where it occurs with the valves united and evidently in situ, [Russia, Sweden, Canada.]
Loc., living. Seas of Greenland, Iceland, and Boreal America.
​77. Pecten maximus (Ostrea sp.), Linnæus.
Loc., fossil. Ireland, rare.
Loc., living. Celtic and Scandinavian Seas.
78. Pecten opercularis (Ostrea sp.), Linnæus.
Syn., P. plebeius and sulcatus of the Mineral Conchology.
Loc., fosssil. Clyde beds. Mammaliferous crag of Southwold.
Loc., living. Throughout the European Seas.
Note. Is found fossil in both coralline and red crags.
79. Pecten varius (Ostrea sp.), Linnæus.
Loc., fossil. Scotland? Wexford, but very rare. [Sweden.]
Loc., living. Throughout the European Seas.
80. Pecten sinuosus (Ostrea sp.), Linnæus.
Syn., Pecten striatus of the Mineral Conchology (fossil in the red and coralline crags) can scarcely be distinguished from this species. Pecten distortus, Montagu. Pecten pusio, Pennant The young shell is the Pecten pusio of Turton, and Pecten spinosus of Brown. It can scarcely be distinguished from the adult Mediterranean pusio.
Loc., fossil. Ireland. The Clyde.
Loc., living. Celtic and Scandinavian Seas.
81. Pecten triradiatus, Muller.
Syn., P. obsoletus of British authors.
Loc., fossil. In the mammaliferous crag of Bramerton. Loch Lomond beds.
Loc., living. Celtic and Scandinavian Seas.
Note. Occurs in the red crag.
82. Ostrea edulis. Linnæus.
Loc., fossil. Frequent in the drift of Scotland and Ireland.
Loc., living. Seas of Celtic and Northern Europe. Coast of the United States (if identical with Ostrea borealis). Dr. Gould says, "The oystermen maintain that our shell is identical with the English O. edulis; and there are certainly forms in which the American and European specimens could not be distinguished."—Invertebrata of Massachusetts, p. 138.
Note. In the coralline crag. Nyst enumerates it among the Campinian fossils of Belgium.
83. Anomia ephippium, Linnæus.
Loc., fossil. English and Irish drift, and Sweden.
Loc., living. Throughout the seas of Europe. Coasts of the United States and Canada.
84. Anomia squamula, Linnæus.
Syn., (var.) Anomia aculeata, Gmelin.
Loc., fossil. Irish drift. Bridlington.
Loc., living. Throughout the European Seas, and on the coast of Boreal America.
Gasteropoda.
85. Dentalium entalis, Linnæus.
Loc., fossil. Isle of Man. North of England. Wales. Ireland. Bridlington.
​Loc., living. General in the European Seas.
Note. "Dentalium dentalis" has been recorded as a pleistocene shell from Bamff, and "Dentalium striatum" from Preston. By the former Dentalis is probably meant. What the Preston shell was it is difficult to say without an examination of the specimens.
86. Patella vulgata, Linnæus.
Loc., fossil. Usually in the sandy and gravelly beds of the British pleistocene. [Sweden.]
Loc., living. In the Northern and Celtic regions of the European Seas.
Note. Appears in the reg crag. It is enumerated by Phillippi with a mark of doubt as an inhabitant of the Sicilian Seas during the Newer Pliocene epoch.
87. Patella pellucida, Linnæus.
Loc., fossil. Clyde beds, Dalmuir.
Loc., living, Celtic and northern regions of the European Seas. Constantly in the Laminarian zone.
88. Patella lævis, Pennant.
Syn., Patella cærulea, Montagu.
Loc., fossil. Ireland. Bamff.
Loc., living. Celtic and northern regions of the European Seas, with the last. The distribution of this species and of Patella pellucida depends probably on that of the Laminariæ, on the leaves or in the root of which fucus they live. Their presence in an upheaved bed is an excellent indication of the depth at which it was formed.
[89. Lottia testudinalis (Patella sp.), O. F. Muller.
Syn., Patella tessellata, Muller. Z. D. Patella Clealandi, Sowerby. Patella clypeus, Brown. Patella amœnay, Say.
Loc., fossil. Sweden.
Loc., living. The seas of Northern and Arctic Europe. Greenland and Boreal America.]
90. Lottia virginea, Muller.
Syn., Patella parva, Da Costa, var. Patella aqualis (Sowerby in Min. Conch.).
Loc., fossil. Scottish beds, frequent. Ireland, rare. [Sweden.]
Loc., living. Celtic and northern regions of the European Seas.
Note. In the coralline and red crags. [Is Lottia parvula this species?]
91. Fissurella græca (Patella sp.), Linnæus.
Syn., Fissurella reticulata, Donovan. Fissurella cancellata, Wood.
Loc., fossil. Clyde beds. [Sweden.]
Loc., living. Throughout the European Seas.
Note. In both red and coralline crags,
92. Cemoria noachina (Patella sp.), Chemnitz.
Syn., Patella fissurella, Muller. Cemoria Flemingii, Leach. Puncturella noachina, Lowe. Sipho striata, Brown.
Loc., fossil. Clyde and other beds in Scotland. [Sweden, Norway.]
Loc., living. Seas of Northern and Arctic Europe, Greenland, and Boreal America.
​93. [Emarginula crassa, Sowerby (M. C.)
Loc., fossil. Norway.
Loc., living. Scandinavian and Scottish Seas.]
94. [Capulus hungaricus (Patella sp.), Linnæus.
Hisinger enumerates this species found living in all the European Seas, among the drift fossils of Sweden.]
95. Velutina lavigata (Helix sp.), Linnæus.
Syn., Helix haliotoidea, Otho Fabricius. Bulla veluiina, Muller. Velutina capuloidea, Blainville. Velutina rupicola, Conrad.
Loc., fossil. Drift beds of Scotland and Ireland. Mammaliferous crag of Bramerton.
Loc., living. Seas of Celtic, Northern and Arctic Europe, Greenland and Boreal America.
Note. Occurs in the red crag.
96. Velutina elongata, Forbes and Goodsir.
Syn., Velutina lanigera, Möller?
Loc., fossil. Mammaliferous crag of Thorpe, according to Mr. Searles Wood.
Loc., living. Scottish Seas, very rare.
97. Velutina undata, Smith.
Syn., Velutina zonata, Gould.
Loc., fossil. Seas of Boreal America.
Loc., living. Clyde beds. [Canada.]
98. Lacuna Montacuti, Turton.
Syn., Helix lacuna, Montagu. Lacuna neritoidea, Gould?
Loc., fossil. Ireland.
Loc., living. Seas of Celtic and Northern Europe. Coast of Massachusetts.
99. Lacuna vincta (Helix sp.), Montagu, and β. Canalis, Turton. Lacuna pertusa, Gerrard.
Loc., fossil. Dalmuir, Bute.
Loc., living. Celtic and Northern Sees. Seas of Boreal America. The distribution of the Lacuna is coextensive with that of the Laminariæ.
100. Littorina littorea (Turbo sp.), Linnæus.
Loc., fossil. In the glacial beds of England and Ireland. Mammaliferous crag of Bramerton. Bridlington. [Sweden, Russia.]
Loc., living. Celtic and Northern regions of the European Seas.
Note. Numerous varieties, which have received as many names in Woodward's 'Geology of Norfolk,' occur in the red crag.
101. Littorina rudis (Turbo sp.), Maton.
Syn. (var). Turbo jugosus, Maton. Turbo obligatus, Say. β. Littorina tenebrosa (Turbo sp.), Maton.
Loc., fossil. Scottish, English; and Irish beds [Sweden].
Loc., living. Celtic, Northern and Arctic regions of the European Seas Coasts of Boreal America.
102. Littorina palliata, Say.
Syn., Turbo expansus, Brown and Smith. Littorina arctica, Möller.
​Loc., fossil. Clyde beds. [Canada.]
Loc., living. Arctic Seas, and coasts of Boreal America.
103. Rissoa semicostata (Turbo sp.), Montagu.
Loc., fossil. Mammaliferous crag of Bramerton.
Loc., living. Celtic Seas.
Note. The species is found in the red crag.
104. Rissoa sub-umbilicata (Turbo sp.), Montagu.
Syn., Turbo minutus, Woodward.
Loc., fossil. In the mammaliferous crag of Bramerton.
Loc., living. Celtic Seas.
105. Scalaria groenlandica (Turbo sp.), Chemnitz.
Var. β. similis, Sowerby (M. C). Scalaria subulata, Couthouy.
Loc., fossil. Mammaliferous crag of Thorpe; Bridlington, Ireland? [Sweden, Canada].
Loc., living. Seas of Greenland and Boreal America.
106. [Scalaria borealis.
Loc., fossil. Canada, Sweden.
Loc., living. Arctic Seas.]
107. Turritella terebra (Turbo sp.), Linnæus.
Syn., Turritella communis, Risso. Turritella Linnæi, Deshayes.
Loc., fossil. General in the pleistocene beds of Britain. Mammaliferous crag of Bramerton, Bridlington.
Loc., living. Generally distributed through the European Seas.
Note. Occurs in both coralline and red crags.
108. Turritella incrassata, Sowerby (M. C).
Syn., Turriiella triplicata, Brocchi.
Loc., fossil. In the glacial beds of Wexford, not rare.
Loc., living. In the Lusitanian and Mediteranean Seas.
Note. This species appeared in our area during the Coralline Crag epoch. It occurs in the red crag. In the drift it is only found towards its southernmost limits. At the close of the Glacial epoch, it retired to more southern seas, and is now abundant on the coast of the south of Spain. Both fossil and recent specimens vary extremely, the whorls presenting every degree of convexity, and in some examples being quite flat. The number and form of the spiral ridges vary, but in every case the interstices are finely striated.
109. Cerithium punctatum, Woodward.
Loc., fossil, Bramerton.
Note. Not known living. A red crag species.
110. Aporrhais pes-pelecani (Strombus sp.), Linnæus.
Loc., fossil, Dalmuir. Ireland.
Loc., living. Throughout the Northern Celtic, Lusitanian, and Mediterranean provinces of the European Seas.
Note. Appears in British area during the Coralline Crag epoch. Is found in the red crag.
111. Murex erinaceus. Linnæus.
Loc. fossil. Scottish and Irish beds. Mammaliferous crag, near Norwich.
​Loc., living. Throughout the seas of Western Europe. The Mediterranean.
112. Fusus muricatus (Murex sp.), Montagu.
Syn., Fusus echinatus, Phillippi (an Sowerby?). Fusus variabilis, De Cristoforis and Jan (^de Phillippi).
Loc., fossil. County of Wexford.
Loc., living. Throughout the European Seas. Seas of Boreal America.
113. Fusus Barvicensis, Johnston.
Loc., fossil. Irish drift.
Loc., living. Northern coasts of Britain.
114. Fusus Bamffius (Murex sp.), Donovan.
Loc., fossil. One of the most generally diffused and abundant species in the British and Irish glacial beds.
Loc., living. Northern and Arctic regions of the European Seas. Common on the Scottish coasts. Greenland. Seas of Boreal America.
115. Fusus scalariformis, Gould.
Syn., Fusus Peruvianus, Lamarck. Fusus lamellosus, Sowerby. Fusus costatus, Hisinger.
Yar. β. Fusus imbricatus, Smith.
Loc., fossil. In the Scotch and Irish glacial beds, of which with the last it is a very characteristic fossil. Bridlington. [Sweden, Russia.].
Log., living. In the Arctic Seas. Greenland. Seas of Boreal America.
Note. A red crag fossil.
116. Fusus Fabricii, Beck (fide Möller).
Syn., Murex craticulus, Otho Fabricius.
This beautiful species, which was not observed in the drift beds until found in Ireland by Captain James, is intermediate in its character between Fusus scalariformis and Fusus Barvicensis. It has the general form and ventricose whorls of the former, with the fimbriated ribs of the latter. In the above cut, from a drawing by Mr. W. Bailey, specimens of natural size are represented by the two uppermost figures, and magnified views by the two lower.
​Loc., fossil. Drift beds of Wexford.
Loc., living. Seas of Greenland.
117. Fusus, nov. sp.? or variety of F. crispus, Brocchi.
A shell measuring above an inch in length, fusiform, the whorls narrow, and crossed by prominent ribs which are traversed by raised spiral ridges. The characters are those of Fusus crispus, of which it is probably an extreme form; but more perfect specimens are required for accurate determination. It is very distinct from any recorded drift fossil.
Loc., fossil. Wexford.
Loc., living. Fusus crispus is at present a Mediterranean species. It occurs fossil in the sub-Appennine beds.
118. Fusus Forbesi, Strickland. [According to Mr. G. Sowerby, identical with Fusus cinereus of Say, an American species synonymous with the Buccinum plicosum of Menke.]
Loc., fossil. Isle of Man.
Loc., living. Coasts of United States.
119. Fusus Sabini. Gray.
Syn., (var.) Fusus ventricosus, Gray?
Loc., fossil. Irish drift. Bridlington.
Loc., living. Banks of Newfoundland. Arctic Seas. Zetland. Closely resembles the following species.
120. Fusus Islandicus, Martini.
Syn., Fusus comeus of British authors, but not of Linnaeus. Fusus angustus, S. Wood.
Loc., fossil. Irish drift.
Loc., living. Common in the Celtic, Northern, and Arctic Seas. Greenland. Coasts of Boreal America.
121. Fusus despectus, (Murex sp.), Linnæus.
Syn., Fusus carinatus, Lamarck.
Fusus striatus, var. carinatus, Sowerby (M.C.).
Fusus tornatus Gould. Tritonium fornicatum, Fabricius.
Loc., fossil. In the mammaliferous crag of Bramerton. Dalmuir. Bridlington: a specimen from the last locality in Mr. Bowerbank's collection is reversed, and frequently ribbed like the Fusus decemcostatus of Say. [Russia, Canada.]
Loc., living. Very rare in the British Seas. Arctic Seas. Greenland. Seas of Boreal America.
122. Fusus antiquus. (Tritonium sp.), Muller.
Syn., Murex despectus, Montagu.
(Reversed variety.) Fusus contrarius. (Murex sp.), Sowerby (in M.C.).
Loc., fossil. Both forms are found in the Irish drift, but chiefly (in the south) the reversed variety. The normal form occurs in the Scotch beds. Mammaliferous crag of Bramerton.
[In the Sicilian newer pliocene beds, the reversed variety is found, though both forms are now extinct in the Mediterranean regions.]
Loc., living. Celtic, Northern, (and Arctic?) Seas of Europe; rarely reversed.
​Note, The reversed variety is found in the Campinian beds of Belgium.
123. Pleurotoma turricula. (Murex sp.), Montaga.
Syn., Murex angulatus, Donovan. Pleurotama Woodiana, Möller.
Loc., fossil. A very variable species, common in the Scotch and Irish beds. Also in the north of England and Isle of Man. In the Bridlington beds, where there are several curious varieties, possibly identical with some of the supposed species into which Möller ('Index Molluscorum Groenlandiæ') has divided this Pleurotoma, In the mammaliferous crag of Bramerton.
Loc., living, Celtic, Northern, and Arctic provinces of the European Seas. Greenland and Boreal America.
Note. It occurs in the red crag.
124. Pleurotoma discrepans, Brown.
Syn., Pleurotoma decussata, Couthouy?
Loc., fossil. Dalmuir.
Loc., living, Scottish Seas, very rare. Seas of Boreal America (if decussata).
125. Pleurotoma septangularis (Murex sp.), Montagu.
Loc., fossil. Ireland.
Loc., living. British Seas.
126. Pleurotoma rufa (Murex sp.), Montagu.
Loc., fossil. Ireland. Mammaliferous crag of Thorpe.
Loc., living. British Seas. Seas of Boreal America.
127. Pleurotoma sp.
Loc., fossil. A small, tapering, smooth species, from Wexford, closely resembling a form now living among the Channel Isles, but too imperfect for determination.
128. Pleurotoma sp.
A small species nearly allied to Pleurotoma linearis. The whorls are convex, spirally furrowed, and strongly ribbed longitudinally. The ribs on the body whorl are twelve. More perfect specimens are required. From Wexford.
129. Buccinum undatum, Linnæus; and var. β. tenerum (M. C).
Loc., fossil. Common in the glacial beds of Britain and Ireland, varying from the strong and coarsely-ribbed normal form to thin and slightly-undulated varieties, which can scarcely be distinguished from the next species. Buccinum striatum of Smith appears to be one of these varieties. Bridlington.
[Sweden, Russia. During the same epoch it inhabited the Mediterranean, but no longer lives there now.]
Loc., living. Celtic, Northern and Arctic regions of the European Seas. Coasts of Boreal America, from Cape Cod northwards.
Note. It appeared within our area during the Coralline Crag epoch.
130. Buccinum ciliatum. Fabricius.
Syn. [A variety] Buccinum Humphreysianum, Bennett Possibly Buccinum fusiforme of Broderip, may be an extreme form of this species.
Loc., fossil. North of England and Scotland. ​Loc., living. Very rare in the British Seas. Common in Arctic Seas and on the banks of Newfoundland.
131. Purpura lapillus (Buccinum sp, Linnæus.
Loc., fossil. Abundant in the sandy (upper) beds of the Irish drift. Common also in England and Scotland. Mammaliferous crag of Bramerton.
Loc., Living in the Celtic, Northern, and Arctic regions of the European Seas. (Replaced in the Lusitanian provinces by Purpura hæmastoma). Greenland; E. coast of America from Florida to the Arctic Seas.
Note. This is one of the most variable of univalve testacea. Well may Dr. Gould remark, that scarcely two specimens can be found alike. I fully agree, after examining long suites of specimens, with Mr. Searles Wood in referring Buccinum crispatum of the Mineral Conchology, and the Murex angulatus, M. lapilliformis, and M. compressus, of Woodward, to this species; nor does the Purpura incrassata of Sowerby appear to be more than a variety. It is probable that the Purpura lapillus is of American origin, and that it was introduced to the European shores during the course of events which brought about the peculiarities of the Pleistocene epoch.
132. Nassa monensis, Forbes.
Loc., fossil. In the pleistocene beds of the north of the Isle of Man. Described by Mr. Strickland in the fourth volume of the 'Proceedings of the Geological Society.' Not known as a living species.
133. Nassa pliocena, Strickland.
Loc., fossil. In the pleistocene beds of the north of the Isle of Man. Described by Mr. Strickland in the fourth volume of the 'Proceedings of the Geological Society.' Not known as a living species.
134. Nassa reticulata, Linnæus.
Loc., fossil. In the Scotch, Manx, Lancashire, and Irish beds.
Loc., living' Throughout the Northern, Celtic, and Lusitanian regions of the European Seas.
135. Nassa semistriata, Brocchi.
Syn., Buccinum labiosum, Sowerby.
Loc. In the Wexford beds.
Loc., living. In the depths of the Ægean.
Note. This is a very abundant tertiary fossil in the miocene beds of Touraine, &c. It is found in the coralline and red crag, and occurs in the Newer Pliocene beds of Sicily and Rhodes.
136. Nassa granulata, Sowerby (M. C).
Loc., fossil. In the mammaliferous crag of Bramerton. In Ireland, at Killiney.
Note. A red crag fossil.
137. Nassa incrassata (Tritonium sp.), Muller.
Syn., Nassa macula (Buccinum sp.), Montagu.
Loc., fossil. Common in all the glacial beds of Britain and Ireland.
Loc., living. In the Northern, Celtic, and Lusitanian regions of the European Seas, but chiefly in the two first. It ranges to Madeira.
Note, A red crag fossil.
​138. Trichotropis borealis, Sowerby.
Syn., Fusus carinatus, jun. Laskey.
Fusus umbilicatus, Smith and Brown.
Trichotropis acuminatus, Jeffreys.
Trichotropis costellatus, Couthouy.
Loc., fossil. Ireland. Bridlington. [Canada.]
Loc., living. Seas of Scotland, Scandinavia, Arctic Seas, Greenland, coasts of America from Massachusets northwards.
Note. A coralline crag fossil.
139. Cancellaria costellifer (Murex sp.), Sowerby (M. C).
Syn., Cancellaria buccinoides, Couthouy. Cancellaria Couthouyi, Jay.
Loc., fossil. Bridlington.
Loc., living. Inhabits the E. coast of America, from Masaachusets to the Arctic Seas.
Note. This species appeared in our area during the Coralline Crag epoch, and continued during the formation of the red crag. It is now restricted to the other side of the Atlantic. It is essentially a Boreal form, though the genus is sub-tropical.
140. Mitra species: an Mitra cornea, Lamarck?
Loc., fossil. A single specimen of a Mitra has occurred in the glacial beds of Wexford. It is too much broken to determine the species, but having the columella entire, with the folds perfectly preserved, there can be no question respecting the genus. Its proportions, and the number, &c., of the folds on the lip approach so nearly to those of Mitra cornea that I have little doubt better specimens will prove the fossil to have been identical with that species. 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 shell before us does away with the anomaly, for we now find in the very beds which were deposited in a sea, the fauna of which was most nearly related to that of Greenland now, a Mitra linking, as it were, the true seat of the genus in the southern and tropical regions, with its outpost in the far north.
Loc., living. Mitra cornea is a characteristic species of the Mediterranean and Lusitanian regions of the European Seas. It occurs fossil in the newer pliocene beds of Sicily.
141. Tornatella pyramidata, (Auricula sp.), Sowerby (M. C.).
Loc., fossil. A well-marked, large, and entire specimen of this fine species has been found in the Wexford beds.
142. Cypræa Europæa, Linnæus.
Loc., fossil. Irish drift.
Loc., living. Throughout the European Seas.
​[The basal portion of a Cypræa as large as Cypræa moneta has been brought to Captain James as having been found in the Wexford drift. As, however, there is something about its aspect which renders it doubtful whether it be not a fragment of a recent shell, I think it better to give merely this notice of it for the present.]
143. Natica monilifera, Lamarck.
Syn. Natica glaucina of British authors. Perhaps identical with N. castanea of Lamarck. Natica glaucinoides of Sowerby (M. C.), not of Deshayes, as pointed out by Mr. Searles Wood, who has named the crag fossil N. catenoides, I am induced to regard the crag and drift forms as one species, and as identical with the living British monilifera. The furrow round the spire is certainly owing to a process of decortication produced during decay. N. fragilis, Smith, appears to me to be the same much decayed.
Loc., fossil. In the Scotch, English, Manx, and Irish glacial beds, frequent. In the mammaliferous crag at Bramerton. [Sweden.]
Loc., living. In the Celtic and Northern (and Lusitanian) regions of the European Seas.
Note. In both the coralline and red crag.
144. Natica sp. nov.? (Bowerbankii, Forbes, MSS.)
In Mr. Bowerbank's Bridlington collection there is an imperfect specimen of a very distinct species of Natica, which does not agree with any living or fossil species known to me. It has a smooth ventricose body whorl, angulated above, and a depressed spire. It equals the Natica monilifera in size.
145. Natica Alderi, Forbes.
Syn. Natica catena of many British authors. Natica anglica of some catalogues.
Loc., fossil. Scottish and Irish drifts.
Loc., living. Northern, Celtic, and Lusitanian regions of the European Seas.
Note. A red crag fossil.
146. Natica helicoides, Johnston.
Loc., fossil. In the mammaliferous crag of Bramerton.
Loc., living. Seas of the north and east of Scotland.
Note. A red crag species. Much more plentiful fossil than recent.
147. Natica clausa, Broderip and Sowerby.
Syn., Natica consolidata, Couthouy.
Natica septentrionalis, Beck.
Loc., fossil. Scottish, Manx, Irish, and North of England glacial beds. Bridlington (Sweden, Russia, Canada).
Loc., living. Arctic Seas and seas of Boreal America.
Note. This fossil occurs in the red crag.
148. Natica groenlandica, Beck.
Loc., fossil, Bridlington.
Loc., living. Seas of Greenland. Extremely rare in the British Seas.
149. Natica Smithii (Bulbus sp.), Brown.
Loc., fossil. The only specimen ever met with of this most interesting ​shell, a member of the division of ampullariform Natics, was found by the Duchess of Argyle in the pleistocene beds at Ardincaple. That specimen was presented to Mr. Smith, and was figured and described by Captain Brown in the eighth volume of the Wernerian Transactions. It has since, unfortunately, been destroyed. From its delicacy, it is not likely to occur in the more disturbed beds of the drift, but should be looked for in the Clyde beds. It is extremely probable that when an opportunity for comparison may occur, the Bulbus Smithii will be found to be identical with the Natica flava of Gould, a rare living inhabitant of the Newfoundland Bank.
[150. Coriocella perspicuus (Helix sp.), Linnæus.
Syn., Bulla haliotoidea, Montagu. Sigaretus haliotoideus of Fleming.
Loc., fossil. Sweden.
Loc., living. Seas of Europe and Boreal America.]
151. Bulla obtusa, Montagu.
Syn., Bulla minuta, Woodward.
Loc., fossil. Mammaliferous crag.
Loc., living. European Seas.
152. Margarita undulata, Sowerby?
Syn., Trochus inflatus, Smith. Trochus tumidus, Hisinger (not of other authors).
Loc., fossil. Clyde beds. [Sweden.]
Loc., living. Arctic Seas and seas of Boreal America. Very rare in the northern European region.
153. Trochus ziziphinus, Linnæus.
Loc., fossil. In the upper beds of the Irish drift. The variety found is very strongly ribbed spirally, and the ridges slightly nodose. The same variety now lives in Falmouth harbour.
Loc., living. Throughout the Northern, Celtic and Lusitanian regions of the European Seas, but chiefly developed in the two former.
Note, It occurs in the red crag.
154. Trochus exasperatus, Pennant
Syn., Trochus exiguus, Montagu. Trochus crenulatus, Brocchi.
Loc., fossil. One of the southern species which occur in the Wexford beds.
Loc., living. In the southernmost parts of the British Seas, and abundant in the Lusitanian region. Phillippi enumerates it among Ehrenberg's Red Sea shells.
155. Trochus cinerarius, Linnæus.
Loc., fossil. In the Scotch, and rarely in the Irish beds.
Loc., living. In the northern and Celtic regions of the European Seas.
156. Trochus tumidus, Montagu.
Loc., fossil. Dalmuir.
Loc., living. In the northern and Celtic regions of the European Seas.
Articulata.
Cirrhipeda.
1. Balanus communis, Pulteney.
Syn., Lepas balanus, Linnæus. Balanus sulcatus, Lamarck.
​Loc., fossil. In the Scotch and Irish pleistocene beds, not unfrequent. [Russia, Sweden.]
Loc., living. In the northern and Celtic regions of the European Seas.
Note, Fossil in the coralline and red crags.
2. Balanus balanoides (Lepas sp.), Linnæus.
Syn., Balanus vulgaris, Da Costa. B. ovularis, Lamarck.
Loc., fossil. Fragments of this species occur in most of the British pleistocene beds. Mammaliferous crag of Postwick.
Loc., living. European and North American Seas.
Note. A red crag species.
3. Balanus uddevallensis, linnæus.
Syn., Balanus candidus, Wood. Balanus scoticus, Wood.
Loc., fossil. Valves of this species are not unfrequent in the British pleistocene beds. [Sweden, Canada.]
Note, All the British glacial Balani I have yet seen may be referred to the three preceding species. The following, however, have been enumerated in addition, and should be carefully sought for.
Balanus costatus, Clyde.
Balanus rugosus, Clyde.
Balanus punctatus.
Balanus tintinnabulum, (a mistake?)
[4. Balanus miser, Gould.
Loc., fossil. Canada, Mr. Lyell.]
5. Creusia verruca (Lepas sp.), Chemnitz.
Syn., Lepas stromia, Muller. Lepas striata, Pennant.
Loc., fossil. Clyde beds.
Loc., living. European Seas.
Annellida.
Spirorbis corrugatus, Serpula vermicularis and Vermilia triquetra are all enumerated in Mr. Smith's list, as British pleistocene fossils. The necessity of an examination of the operculum, as recently shown by Phillippi, in order to determine the genus to which a shell-bearing annelide belongs, throws doubt on the certainty of these determinations, though none in the reference of the fossils to the species usually so called. It is impossible to determine the genus of several annelides to which the shells usually called Vermilia triquetra belong without having the operculum before us. That operculum may yet be found, and as the most common form of the so-called Vermilia in the British Seas, is the Pomatoceros tricuspis, it will probably prove to belong to that species. If the conclusions of Phillippi be admitted the shells of annelides can have no palæontological bearings further than as affording indications of the presence of their order and class.
Radiata.
Echinodermata.
[1. Echinus neglectus, Lamarck.
Loc., fossil. Uddevalla in Sweden. This is the Echinus figured by Mr. ​Lyell, in the Philosophical Transactions. I have examined the specimens and identified them with the Echinus neglectus.
Loc., living. Zetland and Norwegian Seas.]
[2. Echinus granulatus, Say.
Loc., fossil. Canada.
Loc., living. East coast of North America.]
Zoophyta.
3. Cellepora pumicosa.
Loc., fossil. Ireland.
Loc., living. European Seas.
4. Tubulipora verrucaria (Discopora sp.), Fleming.
Loc., fossil. Largs (Rev. Mr. Landsborough).
Loc., living. Celtic Seas.
Plantæ.
1. Nullipora polymorpha. Ellis.
Loc., fossil. In most of the British pleistocene beds.
Loc., living. Atlantic Ocean.
| Mammalia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . | 5 |
| Pisces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . | 1 |
| Mollusca . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . | 155 |
| Cirrhipeda . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . | 5 |
| Annellida . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . | 3? |
| Zoophyta . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . | 2 |
| Plantæ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . | 1 |
| | 174 |
Note. The mammaliferous crag fossils in this catalogue are enumerated on the authorityof the lists published by Mr. Searles Wood. A great many of the Scotch localities are taken from Mr. Smith's list; the Swedish species are given on the authority of Mr. Lyell and M. Hisinger; the Russian on that of Sir Roderick Murchison; and the North American on that of Mr. Lyell.
* ↑ See Mr. W. Thompson's Reports.
* ↑ The capercailxie, the Lepus variabilis, &c.
* ↑ The following extract from the writings of one of the first of living algologists, Will show that there are botanical grounds for my speculation respecting the gulf-weed. "Authors who have written on this Fucus have much disputed, both respecting its origin, and whether it continues to grow whilst floating about. Nothing at all bearing on the former question has yet been discoyered; for though species of Sargassum abound along the shores of tropical countries, none exactly corresponds with S. bacciferum. That the ancestors of the present bank have originally migrated from some fixed station, is probable; but further than probability we can say nothing. That it continues to flourish and gprow in its present situation is most certain. Whoever has picked it up at sea, and examined it with any common attention, must have perceived, not only that the plants were in vigorous life, but that new fronds were continually pushing out from the old, the limit being most clearly defined by the colour, which, in the old frond, is foxy-brown; in the young shoots pale, transparent olive. But how is it propagated; for it never produces fructification? It appears to me, that it is by breakage. The old frond, which is exceedingly brittle, is broken by accident and the branches, continuing to live, push out young shoots from all sides. Many minute pieces that I have exa-mined, were as vigorous as those of larger size, but they were certainly not seedlings, and appeared to me to be broken branches, all having a piece of old frond from which the young shoots sprung. As the plant increases in size, it takes something of a globular figure, from the branches issuing in all directions, as from a centre. On our own shores we have two species analogous to S. bacciferum in their mode of growth, namely, Fukus Mackayi, and the variety B. sub-scostatus of Fucus vesiculosus (F. balticus, Ag.). Neither of these has ever yet been found attached, though they often occur in immense strata; the one, on the muddy sea-shore, the other, in salt marshes, in which situations, respectively, they continue to grow and flourish; and it is remarkable, that neither has ever yet been found in fructification, in which respect, also, they strikingly coincide with S. bacciferum. And if it be hereafter shown that F. Mackayi is merely F. nodosus, altered by gprowing under peculiar circumstances, may it not be inferred that Sargassum bacciferum,—which differs about as much from Sargassum vulgare as Fucus Mackayi does from Fucus nodosus—is merely a pelagic variety of that variable plant?"—Harvey, Manual of the British Algæ. (1841.) Introduction, pp. xvi. xvii. My friend and colleague, Dr. Joseph Hooker, who has had great opportunities of studying the gulf-weed, believes with Dr. Harvey, that the Sargassum bacciferum is an abnormal condition of Sargassum vulgare. Now as the latter is essentially a coast-line plant, growing on rocks with a very limited vertical range, I propose to account for its abnormal condition as Sargassum bacciferum in the gulf-weed bank on the supposition of the submergence of the ancient line of coast on which it originated.
* ↑ For details on tbe Marine Botany of Britain, consult Mr. Harvey's 'Manual of British Algæ.' The deficiency of such marine Alge as are most characteristic of prorinces on the north-east coast of Britain, is strikingly shown in the account given hy Dr. Dickie, of King's College, Aberdeen, in his paper 'On the Marine Algæ of the vicinity of Aberdeen,' in the 'Annals of Natural History for August, 1844.' Out of 80 British species of Melanospermeæ, 46 are absent from the coast examined. "Among the Fucoideæ, the total absence of Cystoseira will be observed, and scarcely one-half of the British species occur; of Laminariæ, scarcely one-half; of Sporochnoideæ only one-third; the two species of Desmarestiæ being generally distributed in Britain. There is also a great deficiency in the Dictyoteæ, Cutleriæ, Halyseris, Padina, Dictyotæ, and Striaria, being totally absent. Of Ectocarpeæ, about one-half of the British species are found, and three out of five Cherdariæ."—Annals, vol. iv. p. 112.
* ↑ Philosophical Transactions, for 1835.
* ↑ Linnæus, Wast-Gotha Ress, p. 197–98.
* ↑ In this memoir the history of the subject, especially to far as Scotland is concerned, is given so fully, that I have not thought it necessary to enumerate separate papers.
* ↑ Index Molluscorum Groenlandiæ. Hafniæ, 1842.
* ↑ Fauna Groenlandica, 1780.
* ↑ Gould's Invertebrata of Massachusetts, 1841.
* ↑ Report on the Mollusca and Radiata of the Ægean Sea, in Reports of the British Association for 1843.
* ↑ Edinburgh Academic Annual for 1840.
* ↑ See p. 373.
* ↑ In one of the latest published summaries of the state of our knowledge of botanical geography (Endlicher and Unger's 'Grundzüge'), 200 feet is given as the probable lowest limit of the distribution of algæ in depth; and in most botanical manuals, Humboldt's obsenration of the occurrence of Fucus vitifolius, at a depth of 192 feet in the seas of the Canaries is quoted as the extreme instance. The following instances of equal and greater ranges of algæ obserred by myself in the eastern Mediterranean, show how much deeper marine vegetation extends there than in more northern seas:—Codium flabelliforme, 30 fathoms; Microdictyon umbilicatum, 30 fathoms; Rityphlæa tinctoria, 50 fathoms; Chrysymenia uvaria, 50 fiithoms; Dictyomenia volubilis, 50 fathoms; Constantinea reniformis, 50 fathoms; Nullipora polymorpha, 95 fathoms.
* ↑ See the valuable Enumeratio Molluscorum Siciliæ of Dr. Phillippi, especially the Second Part and its Appendix. Abo the papers of that most Judicious naturalist, translated in the first volume of the Journal of the Geological Society. See also my 'Report on the Mollusca and Radiata of the Ægean Sea' in the volume of the British Association Reports for 1843. I may here mention that the boreal Mollusca above named as present in the newer pliocene of Sicily, are not present in the newer pliocene of Rhodes, whilst I have reason to believe that the Red Sea forms are more abundant in the Rhodian tertiaries, than in those of Southern Italy. These facts may afford a due to the probable course of migration of the northern and southern extinct forms found in the Mediterranean newer Pliocene.
* ↑ Reports of the British Association for the Meeting at Bristol.
* ↑ Mr. Lyell first called attention to this important fact of the correspondence of the European and American fauna during the glacial period.
* ↑ Import on the Ægean Invertebrata.
* ↑ Magazine of Natural History, vol. xii. p. 324.
* ↑ This species is found fossil in the Sicilian Newer Pliocene beds. It does not appear to differ essentially from the common living Cyrena of the Nile.
* ↑ The facts respecting the distribution of existing animals and plants in the northern hemisphere, bearing so importantly upon the subject of this essay, which I have attempted thus briefly to sketch out, may be understood much better by the reader if he will consult maps 1 and 4 of the phytological and zoological series, in the 'Physical Atlas' of Mr. Johnston and Professor Berghaus. I should be extremely remiss in duty, if I did not take this opportunity of acknowledging my obligations to that admirable and beautiful publication, which, by bringing vividly before the student the leading features of geography, in connexion with meteorology, geology, and natural history, promises to be of incalculable benefit to the progress of the sciences in Britain.
* ↑ See Richardson's Report on North American Zoology, in the Reports of the British Association for 1836.
* ↑ Consult on this subject the nineteenth chapter of Sir Roderick Murchison's 'Geology of Russia,' and the 'British Fossil Mammalia' of Professor Owen.
* ↑ 'On the Relative Ages of the Tertiary and Post-tertiary Deposits of the Basin of the Clyde.'—Geological Transactions, vol. vi.
* ↑ This conclusion is directly opposed to that of the Swiss glacialists. Professor Agassiz writes, in his essay entitled 'A period in the History of our Planet,' (Edinburgh New Philosophical Journal, vol. xxxv.) as follows:— "A crust of ice covered the superficies of the earthy and enveloped in its rigid mantle the remains of organisms which but a moment before had been enjoying existence on its surface. In a word, a period appeared in which the greater portion of the earth was covered with a mass of frozen water; a period in which all life was annihilated, everything organic was put an end to,—the Glacial period. "This Glacial period is the epoch of separation betwixt the Diluvial period, as it has been termed by geologists and our present period; it is it which, like a sharp sword, has separated the totality of now living organisms from their predecessors, which lie interred in the sand of our plain, or below the ice of our polar regions; lastly, it is it which has left to our times the testimonies of its former greatness upon the tops, and in the valleys of our Alps—the glaciers."—p. 17. "The British Islands, Sweden, Norway, and Russia, Germany and France, the mountainous regions of the Tyrol and Switzerland, down to the happy fields of Italy, together with the continent of Northern Asia, formed undoubtedly but one icefield, whose southern limits investigation has not yet determined. And as on the eastern hemisphere, so also on the western, over the wide continent of North America, there extended a similar plain of ice, the boundaries of which are in like manner still unascertained. The polar ice, which at the present day covers the miserable regions of Spitsbergen, Greenland, and Siberia, extended far into the temperate zones of both hemispheres, leaving probably but a broader or narrower belt around the equator, upon which there were constantly developed aqueous vapours, which again condensed at the poles," &c.
* ↑ I say never again submerged, since I am not acquainted with any instance of the meiocenes of Southern Europe and Northern Africa being capped by subsequent marine beds.
* ↑ In the notes to the first part of his 'Cosmos,' Humboldt quotes a passage in which that wonderful old geographer. Strabo—the accuracy and minuteness of whose observation I have often had occasion to admire when accompanying my friends, Captain Graves and his officers, during their surveying labours on the coast of Asia Minor—distinguishes two kinds of islands, those which have been detached from the mainland, and those which have arisen from the sea. Now, though the islands situated in the region of the Atlantic, between the Gulf-weed bank and the Old World, are in great part of volcanic origin, in each group there are fossillferous strata of sedimentary origin and meiocene age, all so related to the corresponding beds in Europe that they must be undoubtedly regarded as the fragments of the upheaved bed of an uniform shallow meiocene sea. In the Madeira group the tertiary limestone, according to Mr. Smith, forms the base rock of the Isle of San Vincente, and in Madeira itself is elevated to a height of 2,500 feet, "a change," writes the observer, "previous to the ejection of the overlying volcanic products." Mr. Smith states also that there are no evidences, in that island, "of elevation f the land during or subsequent to the volcanic period—though strong indications of subsidence."—(Geol. Proceedings, vol. iii. p. 351.) The meiocene limestone of St. Mary's, in the Azores, which includes Pecten latissimus, and other well-marked fossils, will also probably be found, on examination by a competent observer, to be more ancient than the volcanic rocks of that region. In the Canaries and Cape de Verde Islands there are also tertiary marine strata, apparently of meiocene age, and fragments of the same great sea bed with those in the other East Atlantic Islands. That these islands are all, when geologically considered, parts of one system of land, anciently continuous, and belong to Strabo's first class, agrees with their botanical and zoological character as part of one (the great Mediterranean) province. Their floras are all closely related to those of the nearest mainland, and are also mutually related through endemic plants to each other. Out of 596 species of flowering plants, inhabiting Madeira and Porto Santo, 108 are endemic Out of the 108, 28 are common to Madeira and the Azores. (List collated by Dr. Lemann, kindly communicated by Dr. Joseph Hooker.) In the Flora Azorica of Seubert, 400 (flowering and flowerless) plants are enumerated, of which 50 are stated to be endemic and peculiar to the Azores, 34 extra-European, including 23 common to the Azores and Madeira, or the Canaries, and 316 European. The Azorean researches of Mr. Hewett Watson (see his papers in the Botanical Magazine) add to and correct this list. A writer, evidently well versed in the subject, in the 'Phytologist,' for March, 1846, sums up our present knowledge of the Azorean flora as follows:—"The number of species absolutely limited to the Azores is rather less than stated by Seubert, while the number of species common to them and to Madeira requires to be taken at a higher figure. Speaking in round numbers, we may say that four-fifths of all the species now wild in the Azores are wild also in Europe, from which many of them have been doubtless carried to the Azores by the early settlers. Of the remaining one-fifth, nearly the whole number are peculiar to the Azores, or to the Archipelago of the Atlantic Islands, which includes also Madeira and the Canaries. Some have emigrated to the Azores from the continents of Africa and America." The floras of Madeira and the Canaries indicate their proximity to the ancient bounds of the great Mediterranean flora, to the ancient subtropical African province, of which the Cape de Verde Isles probably present us with fragments. (For the flora of the Canaries see the great work of Webb and Berthollet.) In the Gallapagos Islands we have a group which come under Strabo's second class; and, since they lie not farther from the South American mainland than the Azores do from Europe, and moreover have the advantage of lying in the course of a great current (Humboldt's or the Peruvian current) flowing towards them from the American shores, and therefore likely to be a powerful agent in the diffusion of organic forms, they afford us a good opportunity of comparing the features of organic life in islands of the first class with those in such as are distinctly of the second. The researches of Mr. Darwin and of Dr. Joseph Hooker, have furnished good data for such comparison. What is the result? That in these islands, which were never united with the mainland, we have distinct systems of creatures related to those of the nearest land, by representation or affinity, and not by identity. "The natural history of those islands," writes Mr. Darwin, in his admirable 'Journal of Researches,' "is eminently curious, and well deserves attention. Most of the organic productions are aboriginal creations found nowhere else; there is even a difference between the inhabitants of the different islands; yet all show a marked relationship with those of America, though separated from that continent by an open space of ocean between 500 and 600 miles in width. The Archipelago is a little world itself; or, rather, a satellite attached to America, whence it has derived a few stray colonists, and has received the general character of its indigenous productions; considering the small size of these islands, we feel the more astonished at the number of their aboriginal beings, and at their confined range."—(Second Edition, p. 376.)
* ↑ Consult Chart of the Atlantic Ocean, in Johnston's Physical Atlas.
* ↑ One of the freshwater fishes in the Mundesley beds was identified by Mr. Yarrel with Esox lucius. At present the pike is the only freshwater fish common to Europe and America.