onychius
Could not find onychi in Logeion dictionaries.
onychi Adjective: masculine genitive singular, Adjective: neuter genitive singular of onychius
ŏnychĭus, a, um, adj. [onyx],
- of or belonging to onyx: onychius lapis, i. e. onyx, Tert. adv. Marc. 2, 10.
onichius lapis