Source : Webster's Revised Unabridged Dictionary (1913)

Retinula \Re*tin"u*la\, n.; pl. {Retinul[ae]}. [NL., dim. of NL.
   & E. retina.] (Zo["o]l.)
   One of the group of pigmented cells which surround the
   retinophor[ae] of invertebrates. See Illust. under
   {Ommatidium}.