Page:Geology and Mineralogy considered with reference to Natural Theology, 1837, volume 1.djvu/334

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The Side-Arms become gradually smaller towards the upper extremity of the column. In the P. Briareus (Pl. 52, Fig. 3. and Pl. 53, Fig. 1. and 3.) these amount to nearly a thousand in number. The numerous side-arms of the Briarean Pentacrinite, when expanded, would act as auxiliary nets so retain the prey of the animal, and also serve as hold-fasts to assist it in adhering to the bottom, or to extraneous bodies. In agitated water they would close and fold themselves along the column, in a position which would expose the least possible surface to the element, and, together with the column and arms, would yield to the direction of the current.