Lewis & Short

călycŭlus, i, m. dim. [calyx],

  1. I. a small flower-bud, the cup or calyx of a flower, Plin. 20, 19, 78, § 205; 27, 5, 20, § 37; App. M. 4, p. 143, 16.
  2. II. Transf., the outer skin, hide of animals: echinorum, App. Mag. 35, p. 297, 4.