(n.) A cell which refracts light to cause iridescence, found in the skin of fishes, cephalopods, and certain other animals.
1893 CUNNINGHAM & MACMUNN in Phil. Trans. R. Soc. B. CLXXXIV. 767 The chief features of the iridocytes are their regularity of outline, and their great reflecting power.
From the OED:
(n.) A cell which refracts light to cause iridescence, found in the skin of fishes, cephalopods, and certain other animals.
1893 CUNNINGHAM & MACMUNN in Phil. Trans. R. Soc. B. CLXXXIV. 767
The chief features of the iridocytes are their regularity of outline, and their great reflecting power.