Crinoidea

“ There was also sufficient comprehension of the differences between the main classes of Echinoderms—the sea-urchins or Echinoidea, the starfish or Asteroidea, the brittle-stars and their allies known as Ophiuroidea, the worm-like Holothurians, the feather-stars and sea-lilies called Crinoidea, with their extinct relatives the sac-like Cystidea, the bud-formed Blastoidea, and the flattened Edrioasteroidea—while within the larger of these classes, such as Echinoidea and Crinoidea, fair working classifications had been established. ”

“ The first of these, ‘A Memoir on Pentacrinus Europæus, a recent species discovered in the Cove of Cork’ (1 July 1823, Cork, 4to, 2 plates) , announced the presence of a stalked crinoid in our seas; the discovery that the crinoidea were truly ‘radiata,’ and that (as was shown more fully by a second paper in the ‘Edinburgh New Philosophical Transactions,’ 1836) this pentacrinus was really the young stage of antedon, the feather-star. ”

“ The classification of Crinoidea cannot properly be considered without taking account of fossil forms, but to do so at all adequately is impossible on account of limitations of space. Less regret may be felt because the three specialists in this branch, viz. Bather in England, Springer in America, and Jaekel in Germany, come to fundamentally different conclusions on the subject. If we confine our attention to living forms we may, with P. H. Carpenter, [515] select the stem as the basis of classification. ”

“ Yet it is certain that the differences are mostly only such as belong to species, genera, and families, those minor groups of orders and classes which most distinctly reveal differences of physical condition, while agreements of a very general kind permit nearly all fossil zoophyta to be ranked as analogous to known living tribes. Even for the crinoidea, the most considerable exception, at least one living type is known. ”

“ Cystidea, Crinoidea, Blastoidea, Asteroidea, Ophiuroidea, Echinoidea. As for Holothuroidea, the fossil evidence allows us to say no more than that the class existed in early Carboniferous times, if not before. The second method is to work out by slow and sure steps the lines of descent of the different families, orders, and classes, and so either to arrive at the ancestral form of each class, or to plot out the curve of evolution, which may then legitimately be projected into “the dark backward and abysm of time.” ”

“ The rays are hollow beneath, and furnished with tentacula, by the aid of which the star-fish manages to crawl backwards, forwards, or sideways, as the case may be, any of the rays serving as a leader. These animals are found on the sea-shore, forming large beds, which are washed over by the sea. The Crinoidea, or stone-lilies, of which such curious fossil specimens have been found, are nearly allied to the star-fish. ”

“ Class V. Blastoidea.—Pelmatozoa provided with a well-developed stalk and ovoid bud-like calyx. From the mouth the radial canals run backwards over the calyx, as in Echinoidea, but they give rise to numerous lateral branches, which are supported by free unbranched arms ("fingers") . Special respiratory organs occur on the interradial areas in the form of parallel folds called "hydrospires."
CLASS I. CRINOIDEA
This is the only class which has living representatives. There are twelve recent genera, of which eight retain the stalk throughout life ”

“ Part I.—Republication of Descriptions of Lower Carboniferous Crinoidea from the Hall Collection now in the American Museum of Natural History, with Illustrations of the Original Type Specimens not heretofore Figured. By R. Z. Whitfield. ”

“ The encrinites gradually disappeared from the ancient seas; their species were diminished as the globe became older or modified in its conditions, so that at the present time only a few types remain in our seas—such as the Comatula of the Mediterranean; Pentacrinus, the Medusa's-head of the Antilles; and the European Pentacrinus—all of them very rare, and probably destined soon to disappear, carrying with them the last reminiscence of the zoological races of the ancient world: and here lies the real interest which the Crinoïdea presents to the thinking man. ”

“ Of more than thirty species of Crinoïdeans that prevailed to such enormous extent in the Transition period, nearly all became extinct before the deposition of the Lias, and only one presents the angular column of the Pentacrinite; with this one exception, pent angular columns first began to abound among the Crinoïdeans at the commencement of the Lias, and have from thence extended onwards into our present seas. Their several species and even genera are also limited in their extent ”

“ When we consider the profusion of care, and exquisite contrivance, that pervades the frame of every individual in this species of Pentacrinite, forming but one of many members, of the almost extinct family of Crinoïdeans—and when we add to this the amount of analogous mechanisms that characterize the other genera and species of this curious family,—we are almost lost in astonishment, at the microscopic attention that has been paid to the welfare of creatures, holding so low a place among the 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, [5] a mechanism which shows them all to have formed parts of a well-contrived and delicate mechanical instrument ”

“ O. Jaekel (1894) has divided the crinoids into the orders Cladocrinoidea and Pentacrinoidea, the former being the Camerata of Wachsmuth and Springer (Monocyclica Camerata, Adunata and Dicyclica Camerata of the present classification) , and the latter comprising all the rest, in which the arms are either free or only loosely incorporated in the dorsal cup. In minor points there is fair agreement between the American, German and British authors. The families are extinct, except when the contrary is stated. ”

“ It is the more desirable that all these fossils should be made known, as the family of crinoids is so reduced in our days that we can form no idea of the living animals of that group, of their diversity of form, modification of character, and peculiarity of position, from the living type only. He doubted whether the number of crinoid heads of all species found in Europe, now existing in the Museums of Europe, is one-third the number of those which have been found by a single gentleman in Tennessee in one morning. ”

“ It is apparent that in such classes as those just mentioned, of which only the last ends of the branches are still alive, the origin and nature of many structures can not be elucidated, even by the embryology and comparative anatomy of the recent forms, but only by paleontology. Such a structure is, for instance, the mystifying stem of the crinoids which, by a study of the primitive ancestors of the crinoids among the cystids, is readily recognized as a dorsal evagination of the body. ”

“ Here, again, we have a natural gradation of a series of progressive types. Again, among crinoids, we find, in the older deposits, a variety of species resting upon a stem, while free crinoids begin to appear only during the secondary deposit and prevail, in the present creation, over those attached to the soil. Here, again, we have a series of progressive types developed successively, which are apparently independent of each other and seem to bear no other relation to each than that arising from the general character of the group to which they belong. ”

“ Fossil Crinoids of the United States.—At the meeting of the American Association, 1849, a paper on the fossil crinoids of Tennessee, by Professor Troost, was read by Professor Agassiz. [90] The [Pg 178] species embraced are not less than eighty-eight in number, of which only half a dozen have been described. It is the opinion of Professor Hall that all the silurian formations of New York, previous to the beginning of the geological survey, did not afford more than four or five. Now, about sixty species have been ascertained. ”

“ In them the ab-oral region, which has such a remarkable predominance in the Crinoid, has become depressed; it no longer extends into a stem, nor does it even rise into the calyx-like or cup-like projection so characteristic of the Crinoids,—though, when the animal is living, the ab-oral side of the disk is still quite convex. The disk in the Ophiurans is small in comparison to the length of the arms, and perfectly circular; it does not merge gradually in the arms as in the Star-Fish, but the arms start abruptly from its periphery. ”

“ In some the plates of the stem are all rigid and firmly soldered together; in others they are articulated upon each other in such a manner as to give it the greatest flexibility, and allow the seeming flower to wave and bend upon its stalk. It would require an endless number of illustrations to give even a faint idea of the variety of these fossil Crinoids. There is no change that the fancy can suggest within the limits of the same structure that does not find expression among them. ”

“ The Kaihiku Series of Nelson, New Zealand, has yielded some crinoid stems, but the genus has not yet been determined.
Cretaceous Crinoids.—
In the Lower Cretaceous Limestone of Queensland, at Mitchell Downs and Wollumbilla, a typical Crinoid, closely allied to the living Pentacrinus is found, namely, Isocrinus australis (Fig. 76 F) .
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The Upper Cretaceous opal deposits of White Cliffs in Wilcannia, New South Wales, contain many opalised fossil remains, amongst them being Isocrinus australis, already noticed as occurring in the Lower Cretaceous of Queensland. ”

“ There is no reason to suppose that the central apical plate of certain free-swimming crinoids has any more to do with the distal foot-plate of the larval Antedon stem than has the so-called centro-dorsal of Antedon itself, which is nothing but the compressed proximal end of the stem. As for the supposed basals of Echinoidea, Asteroidea and Ophiuroidea, they are scarcely to be distinguished among the ten or more small plates that surround the anus of Bothriocidaris, which is the oldest and probably the most ancestral of fossil sea-urchins (fig. 5) . ”

“ Stirring the water with these arms, it creates currents by which particles of food are wafted to its mouth. Crinoids are rare at the present time, but they grew in the greatest profusion in the warm Ordovician seas and for long ages thereafter. In many places the sea floor was beautiful with these graceful, flowerlike forms, as with fields of long-stemmed lilies. Of the higher, free-moving classes of the echinoderms, starfish are more numerous than in the Cambrian, and sea urchins make their appearance in rare archaic forms. ”

“ Crinoids flourished here in such numbers that beds of limestone 150 feet in thickness are built practically of crinoidal remains and nothing else. The time represented was long enough to allow of a series of modifications of such extent that the crinoid fauna of the Upper Burlington is very distinct from that of the lower beds of the same formation, while the fauna of the Keokuk differs from both. Here again the paleontologist is favored, not only with a wealth of material, but with an opportunity to note the trend and tendency of things. ”

“ The dominating trilobites, sea-scorpions, and tetracorals of the Paleozoic had disappeared, while the brachiopods and crinoids were greatly modified and more like the forms which live today.
Crinoids became moderately abundant at various times, but in many ways different from their relatives of the preceding era. Some of the largest known species, with stems estimated as fifty feet long, have been found in lower Jurassic rocks. A great abundance of microscopic life is indicated by the frequent occurrence of chalk in the Cretaceous formations. ”

“ As a matter of fact, this is the way the crinoid grows—one of the most wasteful processes of growth in nature. It breaks off one arm and grows two instead; but it cannot increase the number of its arms without discarding an old one. ”

“ Their structure and relations were first elucidated in an essay published by Von Buch at Berlin in 1845. They are usually met with as spheroidal bodies covered with polygonal plates, with a mouth on the upper side, and a point of attachment for a stem b (which is almost always broken off) on the lower. (See fig. 433.) They are considered by Professor E. Forbes as intermediate between the crinoids and echinoderms. The Sphæronites here represented (fig. 433.) occurs in the Llandeilo beds in Wales. [358-A]
Fig. ”

“ The Sea-lilies are so abundant in the Carboniferous rocks, that it has been proposed to call the earlier portion of the period the "Age of Crinoids." Vast masses of the limestones of the period are "crinoidal," being more or less extensively composed of the broken columns, and detached plates and joints of Sea-lilies, whilst perfect "heads" may be exceedingly rare and difficult to procure. In North America the remains of Crinoids are even more abundant at this horizon than in Britain, and the specimens found seem to be commonly more perfect. ”

“ Of the five Orders, Beches-de-Mer, Sea-Urchins, Star-Fishes, Ophiurans, and Crinoids,—or, to name them all according to their scientific nomenclature, Holothurians, Echinoids, Asteroids, Ophiurans, and Crinoids,—the last-named are lowest in structure and earliest in time. Cuvier was the first naturalist who detected the true nature of the Crinoids, and placed them where they belong in the classification of the Animal Kingdom. ”