. Elementary text-book of zoology. Zoology. 230 CffiLENTEBATA. Octactinia and Actinia are distributed in all latitudes. The polyps which build banks and reefs are confined to a zone extending about 28 degrees on either side of the equator, and only here and there extend beyond these bounds. They live for the most part near the coast, and produce there in course of time rocky masses of colossal extent by the accumulations of their stony calcareous frameworks. These masses may form coral reefs (atolls, barrier reefs, fringing reefs}, which are perilous to ship- ping, and may also become the foun
. Elementary text-book of zoology. Zoology. 230 CffiLENTEBATA. Octactinia and Actinia are distributed in all latitudes. The polyps which build banks and reefs are confined to a zone extending about 28 degrees on either side of the equator, and only here and there extend beyond these bounds. They live for the most part near the coast, and produce there in course of time rocky masses of colossal extent by the accumulations of their stony calcareous frameworks. These masses may form coral reefs (atolls, barrier reefs, fringing reefs}, which are perilous to ship- ping, and may also become the foundations of islands. In both cases a gradual alteration of level, the raising of the bottom of the sea, assists the work of the coral animals. The presence of the coral banks in the deep sea is, on the other hand, due. to a continual sinking of the FlG. 178.—Astreea (Goniastrcea) pectinata Ehrbg. (after Klunzinger). sea-bottom The part which the Anthozoa take in the alteration of the earth's surface is considerable. In the present time they protect the coast from the consequences of the breaking of the waves and assist in the formation of islands and rocks by producing immense masses of calcareous matter. In earlier geological epochs they have played a still more important part. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Claus, Carl, 1835-1899; Sedgwick, Adam, 1854-1913; Sinclair, F. G. (Frederick Granville), b. 1858. New York : Macmillan
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1884
