Figure 1
Compound and median eyes of trilobites. (a) Aulacopleura koninckii (Barrande, 1846), Silurian, Czech Republik, partly with shell preserved. (b) Holochroal compound eyes of (a). (c) Compound eye of Gerastos cuvieri (Steininger, 1831), Middle Devonian, Germany. (d) Schizochroal eye of Eldredgeops (Phacops) rana crassituberculata Stumm, 1953, Middle Devonian, USA. (e) A. koninckii, two larval stages. f) Upper specimen with location of the median eyes indicated. (g) Median eyes. (h, g) enlarged). (i) Cyclopyge sibilla Šnajdr, 1982, Ordovician, Morocco; 2 specimens, the lower larval. (j) Relevant specimen of (i). (k, j) Position of the median eyes indicated. (l) Median eyes in (j, k) indicated by white arrows. Yellow arrow: dorsal organ, comp. (h, i). Insert: dark structure in the fossil, which is not a median eye. m) Fully shelled glabella of A. koninckii (insert), no median eyes visible. (n1–4) Left median eye of C. sibilla (l), different contrasts. (o1–4) Median median eye of C. sibilla (l), different contrasts. (p1–4) right median eye of C. sibilla (l), different contrasts.
