Arbacioida are an

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...

of sea urchins, consisting of a single family, the Arbaciidae. They are distinguished from other sea urchins by the presence of five separate plates around the anus. Unlike their close relatives, the Salenioida, all of the tubercles on their tests are of similar size. Genera: *''

Arbacia ''Arbacia'' is a genus of sea urchins, widespread in the Atlantic and eastern Pacific oceans. Species According to the World Register of Marine Species : * '' Arbacia crenulata'' Kier, 1963 † (Miocene, east coast of USA) * '' Arbacia dufresn ...

'' Gray, 1835 *'' Arbaciella'' Mortensen, 1910a *'' Arbia'' Cooke, 1948† *'' Baueria'' Noetling, 1885† *'' Codiopsis''

Agassiz Jean Louis Rodolphe Agassiz ( ; ) FRS (For) FRSE (May 28, 1807 – December 14, 1873) was a Swiss-born American biologist and geologist who is recognized as a scholar of Earth's natural history. Spending his early life in Switzerland, he rec ...

, in Agassiz & Desor, 1846† *'' Coelopleurus''

, 1840a *'' Cottaldia'' Desor, 1856 † *'' Dialithocidaris''

, 1898 *'' Habrocidaris''

& Clark, 1907b *'' Podocidaris''

, 1869 *'' Pygmaeocidaris'' Döderlein, 1905 *'' Sexpyga'' Shigei, 1975 *'' Tetrapygus''

, 1841b

References

* * Extant Middle Jurassic first appearances {{Echinoidea-stub