You're probably right, I changed the name already in all my files. I had found the name in a book along with a picture that quite matched my cactus. And 'microhelia' was quoted as a typical beginners' cactus. So I thought it might be that. Thanks for the hint.
I love all your weeds and everyone else's pictures. Posting can be very tricky sometimes here, so I strictly reduced my comments and replies to avoid annoying rewriting of crooked letters and numbers or re-log-ins even if I wasn't logged out.

[Happened all now]