I finally talked to the guy who made the jellyfish cards, John Holbo. They are not, as I had really really really wanted to believe, authentic. The jellyfish themselves truly are by Victorian biologist and illustrator Ernst Haeckel, but Holbo ‘shopped them together.
Here are the two places I’ve seen that present them as authentic, but both are incorrect (and, honestly, the io9 piece could very well just be very, very understatedly tongue-in-cheek).
Holbo was tickled that some people out there (like me) wanted to think they were real. But some weirdness is too good to be true. You can see all the ones he made at his site here:
He’s got some great design work in his other albums as well, and it’s a fascinating collection to browse.
So let’s shed a tear for authenticity but lift a cup of egg nog for some great images! Thanks, John.