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As these in turn are crushed, the more highly organised Malacostraca take the lead, and primitive specimens of the shrimp and lobster make their appearance. The Echinoderms are still mainly represented by the sea-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. CRUSTACEANS. Trilobites now reach their greatest development and more than eleven hundred species have been described from the rocks of this period.
Thus, there are two species of Cypraea, one of Oliva, two of Mitra, four of the genus Cerithium, six of Fusus, two of Trochus, one of Patella, one of Emarginula, etc.; on the whole, more than thirty univalves, spiral or patelliform. At the same time, some of the accompanying bivalve shells, echinoderms, and zoophytes, are specifically identical with fossils of the true Cretaceous series.
Fishes, fossil and living, echinoderms and glaciers, transfigured themselves under his hand, and at thirty he was already at the zenith of his reputation, recognized by all as one of those naturalists in the unlimited sense, one of those folio copies of mankind, like Linnaeus and Cuvier, who aim at nothing less than an acquaintance with the whole of animated Nature.
The three classes of Radiates, beginning with the lowest, and naming them in their relative order, are Polyps, Acalephs or Jelly-Fishes, and Echinoderms or Star-Fishes and Sea-Urchins.
There is no certainly known extinct order of Protozoa; there is but one among the Coelenterata that of the rugose corals; there is none among the Mollusca; there are three, the Cystidea, Blastoidea, and Edrioasterida, among the Echinoderms; and two, the Trilobita and Eurypterida, among the Crustacea; making altogether five for the great sub-kingdom of Annulosa.
In certain districts, as at Doue, in the Department of Maine and Loire, ten miles south- west of Saumur, they form a soft building-stone, chiefly composed of an aggregate of broken shells, bryozoa, corals, and echinoderms, united by a calcareous cement; the whole mass being very like the Coralline Crag near Aldborough, and Sudbourn in Suffolk.
If there is a type of Echinoderms characteristic of a geological period, it is the genus Micraster of the cretaceous formation, in its original circumscription. No species of this genus is known to have existed during the Tertiary era, and no living species has as yet been made known.
These shells and armors begat a kind of torpor and immobility which has continued down to our day with the echinoderms and mollusks, but the arthropods and vertebrates escaped it by some lucky stroke. Now you and I are here without imprisoning shells on our backs; but how or why did we escape? Bergson does not say. Was it a matter of luck or chance?
If we come now to consider the more partial phosphorescence of the sea, we find that it is due to animals belonging to almost every group of marine forms to Echinoderms, or creatures of the sea-urchin and star-fish type, to Annelid worm, to Medusidæ, or jelly-fish, as they are popularly called, including the "great domes" and the "silvery disks" of the passage above quoted from Professor Martin Duncan, to Tunicates, among which is the Pyrosoma, to Mollusks, Crustaceans, and in very many cases to Actinozoa, or forms belonging to the type of the sea anemone and the coral polyp.
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