Page:Popular Science Monthly Volume 85.djvu/231

Rh bottoms of which are covered with corals, should, state that an upward growth of at least one inch per annum may be expected.

But other studies apart from those upon coral reefs were conducted at the Murray Islands. Dr. Hubert Lyman Clark, of Harvard, found many species of the delicate feathery "sea lilies" or crinoids, which live among the coral heads below low tide. These crinoids were, by some, supposed to be sedentary animals but Dr. Clark found that at least certain forms can swim actively through the water using their long graceful arms as oars. In cretaceous times crinoids were abundant along our own shores but are now common only in the depths of the Atlantic Ocean and in the shallow water of the western tropical Pacific and Malayan region northward to Japan.

There were also great numbers of slender serpent stars, rapidly moving forms which usually live in crevices among the rocks and scuttle off