The eyes of the early Tremadoc olenid trilobite Jujuyaspis keideli Kobayashi, 1936

The morphology of the eyes of the olenid trilobite Jujuyaspis keideli Kobay ashi, 1936, is described and illustrated. Studied specimens come from Early Tremadocian pyritiferous black shales of the Casa Colorada Formation (=Pur mamarca shales) at Purmamarca, Jujuy Province, northwestern Argentina. The eyes are holochroal and proportionately large relative to the overall size of cephalon. They are always found attached to the librigena, showing no pr eserved lenses, only molds of their surfaces. Their molds demonstrate that lenses were numerous, biconvex, hexagonal in outline and arranged in an hex agonal close-packing system. The eye curvature and the disposition of the f acets covering all the visual surface indicate that Jujuyaspis keideli Koba yashi had a visual field wider than that of most benthic olenids. The patte rn of lens arrangement and the poorly developed peripheral zone support pel turine affinities for the species.