Wait — come back!
At first glance, this looks like a painting by Bourguereau gone stark raving mad, or something Frank Frazetta might have done if he'd been a Victorian academic painter. In fact, it's a work from 1878 by Luis Ricardo Falero. Falero did a lot of supernatural-themed paintings with voluptuous nudes, but from what I've seen, this is his masterpiece.
The depth of the image, and the smarmy but delightful eroticism of the scene, are wonderful.
[With thanks to Boing Boing.]