Flower porn: Night Blooming Cereus

I don't know what variety of night blooming cereus this is, nor even what genus. My mom gave it to me. It's in a pot with dozens of thin, ribbed arms hanging down about 3 feet. She also had a climbing cereus, which had  pretty much identical blossoms, but that one never took hold here.

This one blooms in June. The blossoms open right at dusk and are gone by dawn, maybe a dozen or two blossoms in a good year, one or two at time. They are more than a foot across. In moonlight, they are luminous; in porch light, they flare. The stamen and anthers are so heavy, they hang to the bottom of the blossom, and the path to the blossom's interior gapes open.