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.
A calycinal system may be quite apparent in the later Ophiuroidea and in a few Asteroidea, but there is no trace of it in the older Palaeozoic types, unless we are to transfer the appellation to the terminals.
The starfish, brittle-stars and their allies have usually been divided into two classes - Asteroidea and Ophiuroidea, each equivalent to the Holothurioidea or Echinoidea.
The starfish, brittle-stars and their allies (see Starfish) have for the last fifty years usually been divided into two classes - Asteroidea and Ophiuroidea, each equivalent to the Holothurioidea or Echinoidea.