ocularium

plural ocularia · alternative occularium

1. A vision slit in a helmet.

   […] 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, 1901, and Following Day, page 47

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

   1 more example

   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 Canada and Alaska, NRC Research Press, →ISBN, page 865