Venus's slipper vs Venus' slipper

Venus's slipper and Venus' slipper both are nouns.

Word	Noun	Adjective	Verb	Adverb
Venus's slipper	Yes	No	No	No
Venus' slipper	Yes	No	No	No

As nouns, Venus's slipper and Venus' slipper are synonyms defined as:

Venus's slipper and Venus' slipper: any of various orchids of the genus Paphiopedilum having slender flower stalks bearing 1 to several waxy flowers with pouchlike lips

Other synonyms of Venus's slipper include Venus's shoe.

Venus's slipper (noun)	Venus' slipper (noun)
any of various orchids of the genus Paphiopedilum having slender flower stalks bearing 1 to several waxy flowers with pouchlike lips	any of various orchids of the genus Paphiopedilum having slender flower stalks bearing 1 to several waxy flowers with pouchlike lips