The Tornaria larva offers a certain similarity to larvae of Echinoderms (sea-urchins, star-fishes, and sea-cucumbers), and when first discovered was so described.
Klein (1734) to denote the tests of the Echini or sea-urchins; its later use for the animals themselves, or for the whole phylum, was an error in both history and etymology.
Those plates are perhaps constant throughout sea-urchins and starfish (though it would puzzle any one to detect them in certain Silurian echinoids), and they may be traced in some of the fixed echinoderms; but there is no proof that they represent the radials of a simple crinoid, and there are certainly many cystids in which no such plates existed.
12, B); but the sea-urchins present a more difficult problem, on which Bothriocidaris sheds no light.
They do not feed on fish, like true otters, but on clams, mussels, sea-urchins and crabs; and the female brings forth but a single young one at a time, apparently at any season of the year.
North of the Atlas it belongs to the European type, in the south it contains a fauna of oysters and sea-urchins belonging to the facies " africano-syrian " of Zittel.
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 Edrioasteroideawhile within the larger of these classes, such as Echinoidea and Crinoidea, fair working classifications had been established.
Lime is, in fact, absorbed to an enormous extent by fishes, molluscs, crustacea, calcareous algae and sponges, starfishes, sea-urchins and feather stars, many polyzoa and a multitude of protozoa (mainly the foraminifera).