peridinial, a. Zool. (pɛrɪˈdɪnɪəl) [f. mod. Zool. L. Peridīnium, f. Gr. περιδῑνής whirled round, περιδῑνεῖν to whirl round.] Belonging or related to the genus Peridinium (wreath-animalcules), or family Peridiniidæ of infusorians.
Oxford English Dictionary