Lewis & Short

mūrēnŭla (mūraen-), ae, f. dim. [1. murena].

  1. I. A small murena (late Lat.): murenulam strictis manibus tenere, Hier. praef. in Job.
  2. II. Transf., a small necklace resembling a murena: aurum colli sui, quod quidem murenulam vulgus vocat, Hier. Ep. 24, 3; id. in Isa. 2, 3, 18.