奥おう陶とう紀き

noun

Ordovician period

Rare geological term; the standard modern term is オルドビス紀. This kanji form is seldom used outside older or specialized texts.

See also: オルドビス紀

• 奥おう陶とう紀きは古こ生せい代だいの一いち時じ期きで、オルドビス紀