A Manual of Conchology / According to the System Laid Down by Lamarck, with the Late Improvements by De Blainville. Exemplified and Arranged for the Use of Students.

by Thomas Wyatt

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.