Radiated, furnished with rays.
Radicated, is when the shell is fixed by the base to another body.
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.
Retroflected, bent backward.
Retrousse, cocked up, turned up.
Retroverted, turned back.
Retuse, ending in an obtuse sinus.
Rotundated, blunted, or turned at the edge.
Reversed spire, is when the volutions turn the reverse way of a common
corkscrew, or to the sun’s apparent motion.
Revolute, rolled backward.
Ribbed, having longitudinal or transverse ridges.
Ridge, the upper part of a slope.
Rima, the interstice between the valves when the hymen is removed.
Rostrum, the beak; the extension of the shell, in which the canal is
situated.
Rotund, round, circular, spherical.
Rudimentary, the commencement or first elements of anything; generally
applied to the indistinct teeth of shells.
Rufous, of a reddish colour.
Rugose, rugged, full of wrinkles.