The Collaborative International Dictionary
Retinula
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.
Wiktionary
retinula
n. (context biology English) One of the group of pigmented cells that surround the retinophorae of invertebrates.