ocularium

Latin oculārium.

• (US) IPA^(key): /ˌɑk.jəˈlɛɹ.i.əm/

ocularium (plural ocularia)

1. A slit in a helmet through which the wearer could see.
   • 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:

     […] 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  […]

2. An elevated mound or "turret", found in some arachnids and other creatures, which contains simple eyes (ocelli).
   • 2007, Tone Novak, Harvestmen: The Biology of Opiliones, Harvard University Press, →ISBN, page 202:

     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) ...

   • 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:

     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 […]

• occularium

oculārium

1. nominative neuter singular of oculārius
2. genitive plural of oculāris

• ocularium in Charles du Fresne du Cange’s Glossarium Mediæ et Infimæ Latinitatis (augmented edition with additions by D. P. Carpenterius, Adelungius and others, edited by Léopold Favre, 1883–1887)