Fig. 19.—a, Cyathocrinites planus. b, Encrinal stem, with uniform joints. c, Single joint, or wheelstone.
As its name imports, the stone-lily or encrinite had a plant-like form. It consisted of a long stalk fixed by the lower end to the sea-bottom, and supporting above a lily-shaped cup, in which were placed the mouth and stomach ([Fig. 19 a]). The stalk consisted of circular plates (some of them not so thick as a sixpence), having their flat sides covered with a set of minute ribs radiating from the centre, and so arranged that the prominent lines of one joint fitted into corresponding depressed lines of the adhering ones. The centre of each joint was pierced by a small aperture, like the axle of a wheel, which, when the stem was entire, formed part of the long tube or canal that traversed the centre of the stem, and served to convey aliment to the remotest part of the animal. Detached joints have thus a wheel-like appearance (Fig 19 c), and hence their common name of wheel-stones. In many species they were not all of the same diameter, but alternately larger and smaller, as if the stem had been made up of a tall pile of sixpences and threepenny pieces in alternate succession. This variation gives a remarkably elegant contour to the stalk. The flower-shaped cup consisted of a cavity formed of geometric calcareous plates, and fringed along its upper margin with thick calcareous arms, five or ten in number, that subdivided into still more slender branches, which were fringed along their inner side with minute cirri or feelers. All these subdivisions, however fine, were made up of calcareous joints like the stalk, so that every stone-lily consisted of many thousand pieces, each perfect in its organization and delicate in its sculpturing. One species peculiar to the Liassic formation (Extracrinus Briareus) has been calculated to contain one hundred and fifty thousand joints!
The effect of this minute subdivision was to impart the most perfect flexibility to even the smallest pinnule. The flower could instantly collapse, and thus the animals on which the encrinite preyed were seized and hurried to the central mouth. The lower part of the cup, or pelvis, as it is called, contained the stomach and other viscera, and communicated with the most distant part of the body by the central alimentary canal.
But while this continued the general type on which the encrinites were constructed, it received many minor modifications. These were effected chiefly on the form and arrangement of the cup-shaped body and its appendages, and form now the basis of our classification into genera and species. Thus, in the genus known as Platycrinus, the lower part of the cup consists of two rows of large hexagonal or polygonal plates fitting closely into each other, while the upper part rises into a dome-like elevation formed of smaller polygonal plates, which have often a mammillated exterior. The arms sprang from the widest part of the body where the large pieces of the lower cup were succeeded by the small pieces of the upper. In an Irish species (P. triacontadactylus), the arms subdivided into thirty branches, each fringed with minuter pinnules and folding round the central elevated spire, as the petals of a crocus close round its central pistil. In another encrinite (Poteriocrinites conicus), the cup was shaped like an inverted cone, the point being affixed to the summit of the stalk, and the broad part throwing out from its edges the lateral arms. The Woodocrinus macrodactylus had such gigantic arms as well-nigh to conceal the position of the cup, which relatively was very small in size. They sprang from near the base of the cup, five in number, but soon subdivided each into two, the ten arms thus produced being closely fringed with the usual jointed calcareous pinnules.
The size and arrangement of the joints of the stalk also differed in different genera. The Woodocrinus and many others had them alternately broad and narrow, like a string of buttons of unequal sizes; others had all the joints of the same relative diameter ([Fig. 19 b]), so that the stalk tapered by a uniform line from base to point. I may add, that on some specimens of both these kinds of stems, we can notice small, solitary areolæ, or scars, which may mark the points of attachment of cirri, or little tentacles, like those on the stem of the existing Pentacrinite. But though each of these varieties of stem is peculiar to a certain number of genera, there is often so little distinction among the detached fragments, that it becomes difficult, indeed impossible, to assign each to its appropriate individual. We may say, that certain encrinal stalks could not have belonged to a poteriocrinus, and others could never have fitted on to the cup of an actinocrinus; but we cannot often say positively to what species they actually would have fitted. There can, however, be no doubt about their being encrinites, and so we have in them a safe and evident test for the origin of the rock in which their remains occur. But to this I shall afterwards revert.
In the meantime, I would have the reader to fix the stone-lily in his memory as peculiarly and emphatically a marine animal, dwelling probably in the deeper and stiller recesses of the ocean, like the Pentacrinite of existing times. Let him try to remember it, not in the broken and sorely mutilated state in which we find it among the blocks of our lime-quarries, but as it must have lived at the bottom of the carboniferous seas. The oozy floor of these old waters lay thickly covered with many a graceful production of the deep, submarine gardens of
"Violet, asphodel, ivy, and vine-leaves, roses and lilies,
Coral and sea-fan, and tangle, the blooms and the palms of the ocean."
Amid this rich assemblage of animated forms, the stone-lilies must have occupied a conspicuous place. Grouped in thick-set though diminutive forests, these little creatures raised their waving stems, and spread out their tremulous arms, like beds of tulips swaying in the evening air. Their flower like cups, so delicately fringed, must have presented a scene of ceaseless activity as they opened and closed, coiling up while the animal seized its prey, or on the approach of danger, and relaxing again when the food had been secured, or when the symptoms of a coming enemy had passed away. Only from this animated action would one have been apt to conjecture these organisms to be other than vegetable. They lived, too, not in detached patches, like the tulip-beds of the florist, but, to judge from the abundance of their remains, must have covered acre after acre, and square mile 'after square mile, with a dense growth of living, quivering flowers. As one individual died out, another took its place, the decaying steins and flowers meanwhile falling to pieces among the limy sediment that lay thickly athwart the sea-bottom, and contributing, by their decay and entombment, to build up those enormous masses of rock, known as the mountain-limestone, which stretch through Yorkshire and the central counties into Wales.