Lewis & Short

nā̆trix, īcis (once m.: natrix violator aquae, Luc. 9, 720; usually), f. [no].

  1. I. A water-snake: cur deus tantam vim natricum viperarumque fecerit? Cic. Ac. 2, 38, 120.
      1. 2. Trop., of a dangerous person: se natricem educare, Suet. Calig. 11.
    1. B. Transf., a whip, scourge, made of a watersnake’s skin: natibu’ natricem impressit crassam et capitatam, Lucil. ap. Non. 65, 30.
  2. II. A plant: Ononis natrix, Linn.; Plin. 27, 12, 83, § 107.