The most highly specialized of all Coral Crabs, however, are the species of the family Hapalocarcinidae, which modify in various ways the growth of the corals on which they live.
The Coralline Crag is nearly composed of corals and shells, the former almost wholly extinct now; but the latter containing upwards of seventy species still existing in the adjacent seas.
In the general details of their structure, the Lower Silurian Corals do not differ from the ordinary Corals of the present day.
For this reason, the common Lower Silurian Corals are separated to form a distinct group under the name of Rugose Corals or Rugosa.
Supplement to theCorals of the Oolitic Formation' (Palæontographical Society).
The characteristic crustaceans and many of the characteristic fishes of the Old Red are wanting in the Devonian; whilst the corals and marine shells of the latter do not occur in the former.
Corals, just as some so-called Corals will ultimately be removed to the present group.
In other cases, as in the marbles of Devonshire, the matrix is so compact and crystalline that the included corals can only be satisfactorily studied by means of polished sections.
The corals of the Cretaceous series are not very numerous, and for the most part are referable to types such as Trochocyathus, Stephanophyllia, Parasmilia, Synhelia (fig.
Simple corals, therefore, are the skeletons of single and independent polypes; whilst compound corals are the skeletons of assemblages or colonies of similar polypes, living united with one another another as an organic community.
In many secondary corals (Cyclolites, Thamnastraea) the trabeculae are so far separate that the individual bars are easily recognizable, and each looks something like a bamboo owing to the thickening of the two ends of each node.
The theca or wall, which in many corals is not an independent structure, but is formed by the conjoined thickened peripheral ends of the septa.
Epitheca, an offset of the basal plate which surrounds the base of the theca in a ring-like manner, and in some corals may take the place of a true theca.
In many of these so-called rugose forms the septa have a characteristic arrangement, differing from that of recent corals chiefly in the fact that they show a tetrameral instead of a hexameral symmetry.
The septa of modern perforate corals are shown to have a structure nearly identical with that of the secondary forms, but the trabeculae and their nodes are only apparent on microscopical examination.
The structure and classification of polyps, however, were at that time very imperfectly understood, and it was fully a century before the true anatomical characters and systematic position of corals were placed on a secure basis.
Hence in corals in which there is only a single cycle of mesenteries the septa are correspondingly few in number; where several cycles of mesenteries are present the septa are correspondingly numerous.
This has been particularly the case with the group of Palaeozoic corals formerly classed together as Rugosa.
Moreover, there are some modern corals in which the secondary cycle of mesenteries departs from the Actinian plan.
In others the peripheral ends of the septa are united only by bars or trabeculae, so that the theca is perforate, and in many such perforate corals the septa themselves are pierced by numerous perforations.
And so the only other alternative was to suppose that the land had gone down, and at so slow a rate that the corals were able to grow upward as fast as it went downward.
The computations of the rate at which corals grow are so exceedingly variable, that we must allow the widest possible margin for error; and it is better in this case to make the allowance upon the side of excess.
Turning to the animal kingdom, he affirmed the tabulate corals of the Silurian rocks to be wonderfully like those which now exist; while even the families of the Aporosa were all represented in the older Mesozoic rocks.
And we have very good means of knowing that any such rise as this certainly has not taken place in the level of the sea since the time that the corals have been building their houses.
Among Radiates, the Corals were more nearly allied to those of the earlier ages than to those of modern times, and Crinoids abounded still, though some of the higher Echinoderm types were already introduced.
In the lesser Antilles the corals are covered with volcanic productions.
Also, we gazed into the depths of the water, and watched for hours the gambols of the curious and bright-coloured fish among the corals and seaweed.
Now it might occur to the reader that perhaps Laura had been somewhat rudely suggestive in her remarks to Mrs. Oreille when the subject of corals was under discussion, but it did not occur to Laura herself.
Mrs. Oreille--"What lovelycorals you have, Miss Hawkins!
He pointed out that the larger and more massive species of corals flourish best on the outer sides of a reef, whilst the more interiorcorals are killed or stunted in growth by the accumulation of coral and other debris.
Chamisso, was the first to propound a definite theory of the origin of atolls and encircling reefs, attributing their peculiar features to the natural growth of corals and the action of the waves.
Beyond their general utility and value as sources of lime, few of the corals present any special feature of industrial importance, excepting the red or precious coral (Corallium rubrum) of the Mediterranean Sea.
Though corals flourish everywhere under suitable conditions in tropical seas, coral reefs and atolls are by no means universal in the torrid zone.
Among the fossils in the English Corallian rocks corals play an important part, frequently forming large calcareous masses or "doggers"; Thamnastrea, Thecosmilia and Isastrea are prominent genera.
Among the millions of organic forms, from corals up to mammalia of the London and Paris basins, hardly a single secondary species is found.
In popular language, the earliest fossils are corals and shellfish.
South America has warm waters and corals on the north-east, and cold waters and glaciers only on its narrowing southern end.
It should, however, first be stated, that corals are not able to survive even a short exposure in the air to the sun's rays, so that their upward limit of growth is determined by that of lowest water at spring tides.
Quoy mentions this case of the Millepora; and I have heard of stinging corals in the West Indies.
This channel will be more or less deep, according to the rate of subsidence, to the amount of sediment accumulated in it, and to the growth of the delicately branched corals which can live there.
The morn's far spent, and the immortal sun Corals his cheek to see those rites not done.
Both layers were formed as the result of vast accumulations of organic and sandy materials on sea bottoms, and in places are composed largely of the remains of marine life—shells, corals and sponges.
The presence of corals and sharks’ teeth not only indicates that this region was covered on more than one occasion by marine waters, but also suggests that these seas were warm and shallow.
But how are we to account for the corals which are found every day towards Monte Ferrato in Lombardy, with the holes of the worms in them, sticking to rocks left uncovered by the currents of rivers?
Why do we find the bones of great fishes and oysters and corals and various other shells and sea-snails on the high summits of mountains by the sea, just as we find them in low seas?
Some of the calcareous beds are highly fossiliferous; those at Frosterley near Stanhope are full of the remains of corals and the stone is polished as a marble.
Corals from various parts of the world and from different geological formations were subsequently dealt with by Duncan, and he came to be regarded as a leading authority on these fossils.
And that this stone was once part of a coral-reef the corals in it prove at first sight.
In some places the sand was of a beautiful creamy white and as pure as could be, Uncle Dick saying that it was formed out of the corals which were being constantly pounded up by the waves.
She had a handsome string of pink corals round her neck, Sicilian gold earrings hung at her ears, and a crimson silk handkerchief was tied over her dark hair with a knot behind her head.
They are often caused by stepping on the sharp corals when fishing on the reefs, or by splinters of wood piercing the skin of the soles of the feet when walking in the bush.
Whilst I was pausing in the descent to examine the numerous embedded corals in the cliff-face, a huge wave rose over the ledge, swept up the face of the cliff over my head, and carried me off as if I had been a feather.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "corals" in a variety of sentences. We hope that you will now be able to make sentences using this word.
