Allied to the cyathopsis is another and still more beautiful coral, described so long ago as the latter part of the seventeenth century by the Welsh antiquary and naturalist, Lhwyd, under the name of _Lithostrotion_. Although many perfect specimens of it have been found, and it is usually as well preserved as any of its congeners, men of science have been sadly at a loss what to call it. Four or five synonyms may be found applied to it in different works on palæontology. There seems now, however, a tendency to return to the name that old Lhwyd gave it two centuries ago; the family to which it belongs, and of which it is the type, has accordingly been termed the _Lithostrotionidæ_, and the species in question _Lithostrotion striatum_ (Fig. 17). It differed from the cyathopsis in several respects, but chiefly in this, that it lived in little congregated groups or colonies, whereas the cyathopsis, like our own actinia, dwelt alone. [Illustration: Fig. 17.--Lithostrotion striatum.] Each of these colonies was formed of a cluster of hexagonal, or rather polygonal pillars, fitting closely into each other, like the basaltic columns of Fingal's Cave, and springing from a common base at the sea bottom.[30] Each pillar constituted the abode of a single animal, and resembled generally the stalk of the cyathopsis. It had the same minute diverging partitions running from the outer walls towards the centre, and the same thin diaphragms, which, stretching horizontally across the interior of the column at short intervals, marked the successive stages of the animal's growth. Within these partitions, which vary from forty to eighty in number, there runs an inner circular tube with thin lamellæ and diaphragms. The exterior of the columns is ribbed longitudinally by a set of long fine striæ, which give somewhat the appearance of the fluting on a Corinthian pillar. The columns, moreover, are not straight, but have an irregular, wrinkled outline, so that, by a slant light, they look like some old pillar formed of many layers of stone, the joints of which have wasted away, producing an undulating profile in place of the original even one. But in these ancient coral columns there is no blunted outline, no worn hollow; the sculpturing stands out as sharp and fresh, and the wavy curves as clearly defined, as though the creature had died but yesterday. They resemble no order of human architecture, save faintly, perhaps, some of the wavy outlines of the Arabesque. [Footnote 30: Sir Roderick Murchison figures in his _Siluria_, p. 282, a gigantic specimen, which measured two feet four inches in width.]