Retiograptus, [282]
Retiolites, [282]
Retiolitidae, [282]
Retractor muscles, of Aristotle's lantern, [526];
of anterior part of body of Holothuroidea, [568];
of Dendrochirota, [568], [572]
Reusenapparat, [145]
Rhabdocrepid, [215], [224] (Crepis is the term applied to the fundamental spicule by deposition of silica upon which a desma is formed. A desma of which the crepis is uniaxial is called a rhabdocrepid desma)
Rhabdopleura, [617]