I turned to the relevant passage in Joshi's carefully prepared edition and found that the word "cryptic" had displaced my rare butterfly. Just a misprint after all, and not even concealing something particularly interesting.
Rather than take my letdown lying down, I propose to define "scyptic" myself:
scyptic ('skiptik) adj. proceeding from or produced by an unknown sourceThe misprint that gave birth to the word is itself scyptic, for Joshi offers no note to explain how it came about or persisted for so long.
[The saga continues here.]