Cidarina cidaris, common name Adam's spiny margarite, is a species of sea snail, a marine gastropod mollusc in the family Calliotropidae.
The height of the gray to grayish white shell attains 20 mm.
(Original description in Latin by Carpenter) "Testa magna, conica, Turcicoidea, tenui; albido-cinerea, nacreo-argentata; anfr. nucleosis âÂÂ? (decollatis), norm, vii, subplanatis, suturis alte insculptis; superficie spirae tota valide tuberculosa, seriebus tribus, alteris postea intercalantibus; peripheria et basi rotundatis, carinatis; carinis circ. 8, haud acutis, irregularibus, scabris, haud tuberculosis; lacuna umbilicali vix conspicua; apertura subrotundata; labro tenuissimo; labio obsoleto; columella arcuata. "
This species occurs in the Pacific Ocean from Alaska to Baja California.