Sea Urchin

“Apical disc of sea-urchin. In the centre is the periproct bearing the anus; around it are five genital or inter-radial plates (g.), one of which is modified as the madreporite (m.); beyond these five ocular or radial plates (o.); i.r.a., an inter-radial or inter-ambulacral area, with spines only; r.a., a radial or ambulacral area, with spines and openings for tube-feet.” -Thomson, 1916

Keywords

Echinoderm, Madreporite, sea urchin apical disc, sea urchin parts, ambulacral area

Galleries

Sea Urchins and Sea Stars

Source

J. Arthur Thomson, M.A., LL.D. Outlines of Zoology (New York, NY: D. Appleton & Company, 1916)

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