ocularium

Noun

ocularium (plural ocularia)

1. A slit in a helmet through which the wearer could see.
   • […] A CLOSED HELMET, with blued surface; the skull-piece has a high roped comb, a deep visor pierced with the ocularium, bevor with annular piercings […]1901, W. H. Spiller, Catalogue of the Valuable Collection of Armour & Arms Formed by W.H. Spiller ...: Which Will be Sold by Auction by Messrs. Christie, Manson & Woods ... on Wednesday, January 30...
2. An elevated mound or "turret", found in some arachnids and other creatures, which contains simple eyes (ocelli).
   • Ocularium with paired armature; area III usually with a pair of spines or tubercles; femur IV entirely straight and unarmed (Figure 4.29a), posterior ozopore absent or much smaller than anterior ozopore (Brazilian Atlantic forest) ...2007, Tone Novak, Harvestmen: The Biology of Opiliones, Harvard University Press, →ISBN, page 202
   • Ocularium [of Hydrocolus paugus] absent (instar I and II) or present (instar III); maxillary cardo present; prementum subrectangular; labial palpomere 2 subcylindrical; antennomere 2 with a secondary seta in instar II and III larvae; legs without natatory setae […]2000, D. J. Larson, Yves Alarie, Robert Edward Roughley, National Research Council Canada, Predaceous Diving Beetles (Coleoptera: Dytiscidae) of the Nearctic Region, with Emphasis on the Fauna of...