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having space and being freely exposed to the open sea, will grow vigorously and tend to form a continuous ring, whilst the growth of the less massive kinds on the central expanse, will be checked by the sediment formed there, and by that washed inwards by the breakers; and as the space becomes shallower, their growth w... |
by the impurities of the water, and probably by the small amount of food brought by the enfeebled currents, in proportion to the surface of living reefs studded with innumerable craving mouths: the subsi- dence of a reef based on a bank of this kind, would give depth to its central expanse or lagoon, steepness to its f... |
the free growth of the coral, symmetry to its outline:—I may here repeat that the larger groups of atolls in the Pacific and Indian oceans cannot be supposed to be founded on banks of this nature. If, instead of the island in the diagram, the shore of a continent fringed by a reef had subsided, a great barrier-reef, li... |
on the N.E. coast of Australia, would have necessarily resulted; and it would have been separated from the main land by a deep-water channel, broad in proportion to the amount of subsidence, and to the less or greater inclination of the neighbouring coast-land. The effect of the continued subsidence of a great barrier-... |
into a chain of separate atolls, will be noticed, when we discuss the apparent progressive disseverment of the larger Maldiva atolls. We now are able to perceive that the close similarity in form, dimensions, structure, and relative position (which latter point will hereafter be more fully noticed) between fringing and... |
necessary result of the transformation, during subsidence, of the one class into the other. On this view, the three classes of reefs ought to graduate into each other. Reefs having an intermediate character between those of the fringing and barrier classes do exist; for instance, on the S.W. coast of Madagascar, a reef... |
is a broad channel from seven to eight fathoms deep, but the sea does not deepen abruptly outside the reef. Such cases, however, are open to some doubts, for an old fringing reef, which had extended itself a little on a basis of its own formation, would hardly be distinguishable from a barrier-reef, produced by a small... |
and with its lagoon-channel nearly filled up with sediment during a long stationary period. Between barrier-reefs, encircling either one lofty island or several small low ones, and atolls including a mere expanse of water, a striking series can be shown: in proof of this, I need only refer to the first plate at the end... |
more plainly to the eye, than any description could to the ear. The authorities from which the charts have been engraved, together with some remarks on them, are given on a separate page descriptive of the plates. At New Caledonia (Plate II. fig. 5.) the barrier-reefs extend for 150 miles on each side of the submarine ... |
and at their northern extremity they appear broken up and converted into a vast atoll-formed reef, supporting a few low coral-islets: we may imagine that we here see the effects of subsidence actually in progress,—the water always encroaching on the northern end of the island, towards which the mountains slope down, an... |
in the lines of their ancient growth. We have as yet only considered the origin of barrier-reefs and atolls in their simplest form; but there remain some peculiarities in structure and some special cases, described in the two first chapters, to be accounted for by our theory. These consist,—in the inclined ledge termin... |
a second ledge with a wall, round the shores of certain lagoons and lagoon-channels; a structure which cannot, as I endeavoured to show, be explained by the simple growing powers of the corals,—in the ring or bason-like form of the central reefs, as well as of the separate marginal portions of the northern Maldiva atol... |
whole, or of parts of certain barrier and atoll-formed reefs; where only a part is submerged, this being generally to leeward,—in the apparent progressive disseverment of some of the Maldiva atolls,—in the existence of irregularly formed atolls, some being tied together by linear reefs, and others with spurs projecting... |
Chagos bank. Step-formed ledges round certain lagoons.—If we suppose an atoll to subside at an extremely slow rate, it is difficult to follow out the complex results. The living corals would grow up on the outer margin; and likewise probably in the gullies and deeper parts of the bare surface of the annular reef; the w... |
islets, but the accumulation of fresh detritus might possibly prevent their entire submergence. After a subsidence of this very slow nature, the surface of the annular reef sloping gently into the lagoon, would probably become united with the irregular reefs and banks of sand, which line the shores of most lagoons. Sho... |
more rapid movement, the whole surface of the annular reef, where there was a foundation of solid matter, would be favourably circumstanced for the fresh growth of coral; but as the corals grew upwards on its exterior margin, and the waves broke heavily on this part, the increase of the massive polypifers on the inner ... |
the want of water. Consequently, the exterior parts would first reach the surface, and the new annular reef thus formed on the old one, would have its summit inclined inwards, and be terminated by a subaqueous wall, formed by the upward growth of the coral (before being much checked), from the inner edge of the solid p... |
reef. The inner portion of the new reef, from not having grown to the surface, would be covered by the waters of the lagoon. Should a subsidence of the same kind be repeated, the corals would again grow up in a wall, from all the solid parts of the resunken reef, and, therefore, not from within the sandy shores of |
the lagoon; and the inner part of the new annular reef would, from being as before checked in its upward growth, be of less height than the exterior parts, and therefore would not reach the surface of the lagoon. In this case the shores of the lagoon would be surrounded by two inclined ledges, one beneath the other, an... |
abruptly terminated by subaqueous cliffs.* * According to Mr. Couthouy (p. 26) the external reef round many atolls descends by a succession of ledges or terraces. He attempts, I doubt whether successfully, to explain this structure somewhat in the same manner as I have attempted, with respect to the internal ledges rou... |
wanted regarding the nature both of the interior and exterior step-like ledges: are all the ledges, or only the upper ones, covered with living coral? if they The ring or bason-formed reefs of the northern Maldiva atolls.—I may first observe, that the reefs within the lagoons of atolls and within lagoon-channels, would... |
the same manner as the annular rim; and, therefore, we might expect that such lagoon-reefs, when not surrounded and buried by an accumulation of sediment more rapid than the rate of subsidence, would rise abruptly from a greater depth than that at which the efficient polypifers can flourish: we see this well exemplifie... |
the deep lagoons of the Chagos and Southern Maldiva atolls are studded. With respect to the ring or bason-formed reefs of the Northern Maldiva atolls, it is evident, from the perfectly continuous series which exists, that the marginal rings, although wider than the exterior or bounding reef of ordinary atolls, are only... |
also evident that the central rings, although wider than the knolls or reefs which commonly occur in lagoons, occupy their place. The ring-like structure has been shown to be contingent on the breaches into the lagoon being broad and numerous, so that all the reefs which are bathed by the waters of the lagoon, are plac... |
conditions with the outer coast of an atoll standing in the open sea. Hence the exterior and living margins of these reefs must have been favourably circumstanced for growing outwards, and increasing beyond the usual breadth; and they must likewise have been favourably circumstanced for growing vigorously upwards, duri... |
has been subjected; and subsidence with this upward growth of the margins would convert the central space of each little reef into a small lagoon. This, however, could only take place with those reefs, which had increased to a breadth sufficient to prevent their central spaces from being almost immediately filled up wi... |
are the kinds different on the ledges according to the depth? Do the interior and exterior ledges occur together in the same atolls; if so, what is their total width, and is the intervening surface-reef narrow, &c.? driven inwards from all sides: hence it is that few reefs, which are less than half a mile in diameter, ... |
atolls where the bason-like structure is most strikingly exhibited, include lagoons. This remark, I may add, applies to all coral-reefs, wherever found. The bason-formed reefs of the Maldiva Archipelago may, in fact, be briefly described, as small atolls formed during subsidence over the separate portions of large and ... |
the barrier-reefs, which encircled the islands of a large archipelago now wholly submerged. Submerged and Dead Reefs.—In the second section of the first chapter, I have shown that there are in the neighbourhood of atolls, some deeply submerged banks, with level surfaces; that there are others, less deeply but yet wholl... |
consisting merely of dead coral-rock; that there are barrier-reefs and atolls with merely a portion of their reef, generally on the leeward side, submerged; and that such portions either retain their perfect outline, or they appear to be quite effaced, their former place being marked only by a bank, conforming in outli... |
perfect. These several cases are, I believe, intimately related together, and can be explained by the same means. There, perhaps, exist some submerged reefs, covered with living coral and growing upwards, but to these I do not here refer. As we see that in those parts of the ocean, where coral reefs are most abundant, ... |
another neighbouring one is not fringed; as we see in the same archipelago, that all the reefs are more perfect in one part of it than in another,—for instance, in the southern half compared with the northern half of the Maldiva Archipelago, and likewise on the outer coasts compared with the inner coasts of the atolls ... |
which are placed in a double row; as we know that the existence of the innumerable polypifers forming a reef, depends on their sustenance, and that they are preyed on by other organic beings; and, lastly, as we know that some inorganic causes are highly injurious to the growth of coral, it cannot be expected that durin... |
change to which earth, air, and water are exposed, the reef-building polypifers should keep alive for perpetuity in any one place; and still less can this be expected, during the progressive subsidences, perhaps at some periods more rapid than at others, to which by our theory these reefs and islands have been subjecte... |
improbable that the corals should sometimes perish either on the whole or on part of a reef; if on part, the dead portion, after a small amount of subsidence, would still retain its proper outline and position beneath the water. After a more prolonged subsidence, it would probably form, owing to the accumulation of sed... |
flat bank, marking the limits of the former lagoon. Such dead portions of reef would generally lie on the leeward side,* for the impure water and fine sediment would more easily flow out from the lagoon over this side of the reef, where the force of the breakers is less than to windward; and therefore the corals would ... |
vigorous on this side, and be less able to resist any destroying agent. It is likewise owing to this same cause, that reefs are more frequently breached to leeward by narrow channels, serving as by ship-channels, than to windward. If the corals perished entirely, or on the greater part of the circumference of an atoll,... |
rock, more or less entirely submerged, would be produced; and further subsidence, together with the accumulation of sediment, would often obliterate * Mr. Lyell, in the first edition of his Principles of Geology, offered a somewhat different explanation of this structure. He supposes that there has been subsidence; but... |
in most cases, if not in all, dead; and he attributes the difference in height in the two sides of most atolls, chiefly to the greater accumulation of detritus to windward than to leeward. But as matter is accumulated only on the backward part of the reef, the front part would remain of the same height on both sides. I |
may here observe that in most cases (for instance at Peros Banhos, the Gambier group and the Great Chagos bank) and I suspect in all cases, the dead and submerged portions do not blend or slope into the living and perfect parts, but are separated from them by an abrupt line. In some instances small patches of living re... |
to the surface from the middle of the submerged and dead parts. its atoll-like structure, and leave only a bank with a level surface. In the Chagos group of atolls, within an area of 160 miles by 60, there are two atoll-formed banks of dead rock (besides another very imperfect one) entirely submerged; a third, with mer... |
very small pieces of living reef rising to the surface; and a fourth, namely Peros Banhos (Plate I. fig. 9), with a portion nine miles in length dead and submerged. As by our theory this area has subsided, and as there is nothing improbable in the death, either from changes in the state of the surrounding sea or from t... |
subsidence being great or sudden, of the corals on the whole, or on portions of some of the atolls, the case of the Chagos group presents no difficulty. So far indeed are any of the above-mentioned cases of submerged reefs from being inexplicable, that their occurrence might have been anticipated on our theory; and as ... |
be in progressive formation by the subsidence of encircling barrier-reefs, a weighty objection, namely that the number of atolls must be increasing infinitely, might even have been raised, if proofs of the occasional destruction and loss of atolls could not have been adduced. The disseverment of the larger Maldiva atol... |
into smaller ones, is, in many respects, an important consideration, and requires an explanation. The graduated series, which marks as I believe this process, can be observed only in the northern half of the group, where the atolls have exceedingly imperfect margins, consisting of detached bason-formed reefs. The curre... |
by Capt. Moresby, with considerable force, and drift the sediment from side to side during the monsoons, transporting much of it seaward; yet the currents sweep with greater force round their flanks. It is historically known that these atolls have long existed in their present state; and we can believe, that even durin... |
remain, the central expanse being kept at nearly its original depth by the accumulation of sediment. But in the action of such nicely balanced forces during a progressive subsidence, (like that, to which by our theory this archipelago has been subjected,) it would be strange if the currents of the sea should never make... |
of the atolls, through the many wide breaches in their margins. If this were once effected, a deep-water channel would soon be formed by the removal of the finer sediment, and the check to its further accumulation; and the sides of the channel would be worn into a slope like that on the outer coasts, which are exposed ... |
same force of the currents. In fact, a channel precisely like that bifurcating one which divides Mahlos Mahdoo (Plate II. fig. 4.), would almost necessarily be formed. The scattered reefs situated near the borders of the new ocean-channel, from being favourably placed for the growth of coral, would, by their extension,... |
such a tendency is very evident, (as may be seen in the large published chart) in the elongated reefs on the borders of the two channels intersecting Mahlos Mahdoo. Such channels would become deeper with continued subsidence, and probably from the reefs not growing up perpendicularly, somewhat broader. In this case, an... |
originally of considerable breadth, the dissevered portions would become perfect and distinct atolls, like Ari and Ross atolls, (Plate II, fig. 6.) or like the two Nillandoo atolls, which must be considered as distinct, although related in form and position, and separated from each other by channels, which though deep ... |
and the dissevered portions would then resemble Phaleedoo and Moluque atolls, or Mahlos Mahdoo and Horsburgh atolls, (Plate II. fig. 4.) which are related to each other in no respect except in proximity and position. Hence, on the theory of subsidence, the disseverment of large atolls, which have imperfect margins (for... |
are exposed to strong currents, is far from being an improbable event; and the several stages from close relation to entire isolation in the atolls of the Maldiva Archipelago, are readily explicable. We might go even further, and assert as not improbable, that the first formation of the Maldiva Archipelago was due to a... |
with that of New Caledonia (Plate II. fig. 5.): for if, in imagination, we complete the subsidence of that great island, we might anticipate from the present broken condition of the northern portion of the reef, and from the almost entire absence of reefs on the eastern coast, that the barrier-reef after repeated subsi... |
separated into distinct portions; and these portions would tend to assume an atoll-like structure, from the coral growing with vigour round their entire circumferences, when freely exposed to an open sea. As we have some large islands partly submerged with barrier-reefs marking their former limits, such as New Caledoni... |
large islands wholly submerged; and these, we may now infer, would be surmounted, not by one enormous atoll, but by several large elongated ones, like the atolls in the Maldiva group; and these again, during long periods of subsidence, would sometimes become dissevered into smaller atolls. I may add, that both in the M... |
standing close together, which have an evident relationship in form: we may suppose, in such cases, either that two or more encircled islands originally stood close together, and afforded bases for two or more atolls, or that one atoll has been dissevered. From the position, as well as form, of three atolls in the Caro... |
group), which are placed in an irregular circle, I am strongly tempted to believe that they have originated by the process of disseverment.* * The same remark is, perhaps, applicable to the islands of Ollap, Fanadik, and Tamatam in the Caroline Archipelago, of which charts Irregularly-formed Atolls.—In the Marshall gro... |
and Menchicoff atoll is formed of three loops, two of which (as may be seen in fig. 3. Plate II.) are connected by a mere ribbon-shaped reef, and the three together are 60 miles in length. In the Gilbert group some of the atolls have narrow strips of reef, like spurs, projecting from them. There occur also in parts of |
the open sea, a few linear and straight reefs, standing by themselves; and likewise some few reefs in the form of crescents, with their extremities more or less curled inwards. Now, the upward growth of a barrier-reef which fronted only one side of an island, or one side of an elongated island with its extremities, (of... |
produce after the complete subsidence of the land, mere strips or crescent or hook-formed reefs: if the island thus partially fronted became divided during subsidence into two or more islands, these islands would be united together by linear reefs; and from the further growth of the coral along their shores together wi... |
produced, either atolls united together by linear reefs, or atolls with spurs projecting from them. Some, however, of the more simple forms above specified, might, as we have seen, be equally well produced by the coral perishing during subsidence on part of the circumference of an atoll, whilst on the other parts it co... |
the surface. The Great Chagos Bank.—I have already shown that the submerged condition of the Great Chagos bank, (Plate II. fig. 1. with its section fig. 2.) and of some other banks in the Chagos group, may in all probability be attributed to the coral having perished before or during the movements of subsidence, to whi... |
our theory has been sub- are given in the atlas of Duperrey's voyage: a line drawn through the linear reefs and lagoons of these three islands forms a semicircle. Consult also, the atlas of Lutké's voyage; and for the Marshall group that of Kotzebue; for the Gilbert group (which is referred to in the ensuing page) cons... |
Duperrey's voyage. Most of the points here referred to may, however, be seen in Krusenstern's general Atlas of the Pacific. jected. The external rim or upper ledge, (shaded in the chart,) consists of dead coral-rock thinly covered with sand; it lies at an average depth of between five and eight fathoms, and perfectly r... |
an atoll. The banks of the second level, the boundaries of which are marked by dotted lines in the chart, lie from about fifteen to twenty fathoms beneath the surface; they are several miles broad, and terminate in a very steep slope round the central expanse. This central expanse I have already described, as consistin... |
between thirty and forty fathoms deep. The banks of the second level, might at first sight be thought analogous to the internal step-like ledge of coral-rock which borders the lagoons of some atolls, but their much greater width, and their being formed of sand, are points of essential difference. On the eastern side of... |
are linear and parallel, resembling islets in a great river, and pointed directly towards a great breach on the opposite side of the atoll: these are best seen in the large published chart. I inferred from this circumstance, that strong currents sometimes set directly across this vast bank; and I have since heard from ... |
case. I observed, also, that the channels, or breaches through the rim, were all of the same depth as the central lagoon-like space into which they lead; whereas the channels into the other atolls of the Chagos group, and as I believe into most other large atolls, are not nearly as deep as their lagoons:—for instance a... |
channels are only of the same depth, namely between 10 and 20 fathoms, as the bottom of the lagoon for a space about a mile and a half in width round its shores, whilst the central expanse of the lagoon is from 35 to 40 fathoms deep. Now, if an atoll during a gradual subsidence once became entirely submerged, like |
the Great Chagos bank, and therefore no longer exposed to the surf, very little sediment could be formed from it; and consequently the channels leading into the lagoon from not being filled up with drifted sand and coral detritus, would continue increasing in depth, as the whole sank down. In this case, we might expect... |
open sea, instead of any longer sweeping round the submarine flanks, would flow directly through the breaches across the lagoon, removing in their course the finer sediment, and preventing its further accumulation. We should then have the submerged reef forming an external and upper rim of rock, and beneath this portio... |
by deep-water channels or breaches, and thus formed into separate marginal banks; and these would be cut off by steep slopes, overhanging the central space, worn down by the passage of the oceanic currents. By these means, I have scarcely any doubt that the Great Chagos bank has originated,—a structure which at first a... |
any I had met with. The process of formation is nearly the same with that, by which Mahlos Mahdoo has been trisected; but in the Chagos bank the channels of the oceanic currents entering at several different quarters, have united in a central space. This great atoll-formed bank appears to be in an early stage of dissev... |
of subsidence go on, from the submerged and dead condition of the whole reef, and the imperfection of the S.E. quarter, a mere wreck would probably be left. The Pitt's bank, situated not far southward, appears to be precisely in this state: it consists of a moderately level, oblong bank of sand, lying from 10 to 20 fat... |
surface, with two sides protected by a narrow ledge of rock which is submerged between 5 and 8 fathoms. A little further south, at about the same distance as the southern rim of the Great Chagos bank is from the northern rim, there are two other small banks with from 10 to 20 fathoms on them; and not far eastward |
soundings were struck on a sandy bottom, with between 110 and 145 fathoms. The northern portion with its ledge-like margin, closely resembles any one segment of the Great Chagos bank, between two of the deep-water channels, and the scattered banks southward appear to be the last wrecks of less perfect portions. I have ... |
Indian and Pacific oceans, and have now brought before the reader all the examples, which I have met with, of reefs differing from the type of the class to which they belong; and I think it has been satisfactorily shown, that they are all included in our theory, modified by occasional accidents which might have been an... |
this course we have seen, that in the lapse of ages encircling barrier-reefs are occasionally converted into atolls,—the name of atoll being properly applicable, at the moment when the last pinnacle of encircled land sinks beneath the surface of the sea. We have, also, seen that large atolls during the progressive subs... |
become dissevered into smaller ones; at other times, the reef-building polypifers having entirely perished, atolls are converted into atoll-formed banks of dead rock; and these again, through further subsidence and the accumulation of sediment, modified by the force of the oceanic currents, pass into level banks with s... |
from its first origin, through the occasional accidents of its existence, to its destruction and final obliteration. Objections to the theory of the formation of Atolls and Barrier-reefs.—The vast amount of subsidence, both horizontally or in area, and vertically or in depth, necessary to have submerged every mountain,... |
will probably strike most people as a formidable objection to my theory. But as continents, as large as the spaces supposed to have subsided, have been raised above the level of the sea,—as whole regions are now rising, for instance, in Scandinavia and South America,—and as no reason can be assigned, why subsidences sh... |
of the earth's crust on as great a scale both in extent and amount as those of elevation, objections of this nature strike me as of little force. The remarkable point is, that movements to such an extent should have taken place within a period, during which the polypifers have continued adding matter on and above the s... |
and less obvious objection to the theory will perhaps be advanced from the circumstance, of the lagoons within atolls and within barrier-reefs never having become in any one instance during prolonged subsidences of a greater depth than 60 fathoms, and seldom more than 40 fathoms: but we already admit, if the theory be ... |
has not exceeded that of the upward growth of the corals on the exterior margin; we are, therefore, only further required to admit, that the subsidence has not exceeded in rate the filling up of the interior spaces by the growth of the corals living there, and by the accumulation of sediment. As this filling up must ta... |
slowly within barrier-reefs lying far from the land, and within atolls which are of large dimensions and which have open lagoons with very few reefs, we are led to conclude that the subsidence thus counter-balanced, must have been slow in an extraordinary degree;—a conclusion which accords with our only means, namely, ... |
of recent elevatory movements, of judging by analogy what is the probable rate of subsidence. In this chapter it has, I think, been shown, that the theory of subsidence, which we were compelled to receive from the necessity of giving to the corals, in certain large areas, foundations at the requisite depth, explains bo... |
regular forms of those two great classes of reefs, which have justly excited the astonishment of all persons who have sailed through the Pacific and Indian oceans. But further to test the truth of the theory, a crowd of questions will occur to the reader: Do the different kinds of reefs, which have been produced by the... |
movement, generally lie within the same areas? What is their relation of form and position,—for instance, do adjoining groups of atolls, and the separate atolls in these groups, bear the same relation to each other which islands do in common archipelagoes? Have we reason to believe, that where there are fringing reefs,... |
it is almost our only way of ascertaining this point, are there frequently proofs of recent elevation? Can we by this means account for the presence of certain classes of reefs in some large areas, and their entire absence in others? Do the areas which have subsided, as indicated by the presence of atolls and barrier-r... |
have remained stationary or have been upraised, as shown by fringing-reefs, bear any determinate relation to each other; and are the dimensions of these areas such as harmonize with the greatness of the subterranean changes, which, it must be supposed, have lately taken place beneath them? Is there any connection betwe... |
questions ought to receive answers in accordance with the theory; and if this can be satisfactorily shown, not only is the theory confirmed, but as deductions, the answers are in themselves important. Under this latter point of view, these questions will be chiefly considered in the following chapter.* * I may take thi... |
would probably be presented by a vertical and deep section across a coral formation (referring chiefly to an atoll) formed by the upward growth of coral during successive subsidences. This is a subject worthy of attention, as a means of comparison with ancient coral strata. The circumferential parts would consist of ma... |
filled up with detritus; but this would be the part most subject to subsequent denudation and removal. It is useless to speculate how large a proportion of the exterior annular reef would consist of upright coral, and how much of fragmentary rock, for this would depend on many contingencies,—such as on the rate of subs... |
of coral to cover the whole surface, and on the breakers having force sufficient to throw fragments over this same space. The conglomerate which composes the base of the islets, would (if not removed by denudation together with the exterior reef on which it rests) be conspicuous from the size of the fragments,—the diff... |
rounded,—the presence of fragments of conglomerate torn up rounded and recemented,—and from the oblique stratification. The corals which lived in the lagoon-reefs at each successive level, would be preserved upright, and they would consist of many kinds, generally much branched. In this part, however, a very large prop... |
be formed of sedimentary matter, either in an excessively fine, or in a moderately coarse state, and with the particles almost blended together. The conglomerate which was formed of rounded pieces of the branched corals, on the shores of the lagoon, would differ from that formed on the islets and derived from the outer... |
very near each other. I have seen a conglomerate limestone from Devonshire like a conglomerate now forming on the shores of the Maldiva atolls. The stratification taken as a whole, would be horizontal; but the conglomerate beds resting on the exterior reef, and the beds of sandstone on the shores of the lagoon (and no ... |
would probably be divided (as at Keeling atoll and at Mauritius) by numerous layers dipping at considerable angles in different directions. The calcareous sandstone and coral rock would almost necessarily contain innumerable shells, echini, and the bones of fish, turtle, and perhaps of birds; possibly, also, the bones ... |
far remote from any continent. The large shells of some species of Tridacna would be found vertically imbedded in the solid rock, in the position in which they lived. We might expect, also, to find a mixture of the remains of pelagic and littoral animals in the strata formed in the lagoon, for pumice and the seeds of p... |
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