Which preposition to use with skullcap

on Occurrences 1%

I opened my mouth to call Casey's attention to itthough I felt that he was watching it with that steady, squinting stare of his that never seems to wink or waver for a secondbut there it was again, come to a stop just under the crest of the mountain where the white slide was topped by a black rim capped with bleak, bare rock like a crude skullcap on Tippipah.

with Occurrences 1%

" The feather from the wing of Helmas' goose King Ferdinand had caused to be affixed to the unassuming skullcap with a halo of gold wire which Ferdinand now wore in the place of a vainglorious earthly crown; so that perpetual contiguity with this relic might keep him in augmenting sanctity.

Which preposition to use with  skullcap