Page:Geology and Mineralogy considered with reference to Natural Theology, 1837, volume 1.djvu/320

 316 importance among the earliest inhabitants of the ancient deep. The extensive range which it formerly occupied among the earliest inhabitants of our Planet, may be estimated from the fact, that the Crinoïdeans already discovered have been arranged in four divisions. comprising nine genera, most of them containing several species, and each individual exhibiting, in every one of its many thousand component little bones, a mechanism which shows them all to have formed parts of a well-contrived and delicate mechanical instrument; every part acting in due connexion with the rest, and all adjusted to each other with a view to the perfect performance of some peculiar function in the economy of each individual.

The joints, or little bones, of which the skeletons of all these animals were composed, resemble those of the starfish: their use, like that of the bony skeleton in vertebral animals, was to constitute the solid support of the whole body, to protect the viscera, and to form the foundation of a system of contractile fibres pervading the gelatinous integument with which all parts of the animal were invested.

The bony portions formed the great bulk of the animal, as they do in star-fishes. The calcareous matter of these little bones was probably secreted by a Periosteum, which