Glossary
Glossary terms beginning with: R
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- radial water vessel
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A baranch of the water vascular system that runs up the middle of each ambulacrum.
- retractor muscles
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Muscles connecting the pyramids to the perignathic girdle and used to pull the lantern into the test.
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- rosette
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Calcareous elements (usually five) that are arranged in a circle to form the frame of the suckered disc of tube-feet.
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- rostrate (pedicellaria)
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A kind of pedicellaria with strongly curved blades that touch only at their distal tips. Not associated with poison glands.
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- rostrum
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An anterior region of the test that is prolonged and projecting. The picture shows the cassiduloid Archiacia in lateral profile.
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- rotula
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Part of the Aristotle's lantern. A bone-shaped ossicle that forms a brace between adjacent pyramids. It articulates with the epiphyses.
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