Palaeodiscus sentence example
- An Upper Silurian echinoid, however, Palaeodiscus, is believed by W.
- If this be correct, the only change from Edrioaster, as regards the ambulacra, was that in Palaeodiscus the covering-plates could no longer open, but closed permanently over the whole groove, while the podia issued through slits between them.
- Include only Echinocystis, Palaeodiscus and (?) Myriastiches, all Upper Silurian.
- It is, however, quite possible that Echinocystis may some day be referred to the Cidaroida, and Palaeodiscus to the Melonitoida.