Rectangular, having right angles.
Recurvated, turned backward.
Recurved, bowed back.
Reflected, thrown backward, or bent back.
Reflex, } the same as recurvated.
Reflexed, }
Refracted, abruptly bent, as if broken.
Reniform, kidney-shaped.
Repand, with a serpentine margin.
Replicated, folded or plaited, so as to form a groove or channel.
Reticulated, formed like a piece of network.