Subway rider and Flickr photographer extraordinaire Kate Black happened upon a great mythological creature this past weekend. No, she didn't see Bigfoot or the even rarer "single-and-sane-woman thing"; rather, she spotted and took a photo of a creepy subway perv.

The (alleged) pervert, who has yet to be apprehended, boarded a Brooklyn-bound 4 train on Sunday. Black was already on the train, minding her own business with a book or whatever the kids are reading these days.

"He saw two single women (myself and a young woman across from me) in a not very densely populated train car, and entered from an adjacent car while the train was in motion," she says.

He stood near another woman and faced Black first from a few feet away with a boner in his pants. He made no move to take it out, but when Black attempted to take a picture of his face, the man did a 180 and showed another woman and her small child how he dresses to the right.

Keep reading to see another not-so-helpful picture of the alleged culprit and some advice on capturing pervs (on film) from this victim.

Of course, this perv didn't actually flash anyone, but who wants to have creepy old man bone in their face while trying to pretend no one else exists?

"I am quite certain that this would've escalated had I not had a camera," Black says now.

Black's advice for victims of subway indecency is to "change your ISO settings as soon as you go from bright daylight to indoor or underground shooting conditions. If I'd done that, I would've been fast enough to get a photo of his face."

Yes, that and scream bloody murder, ask one of us burly dudes to detain and/or tackle him (just not around the waist) and alert the MTA or the coppers, pronto. Anything less just keeps them coming back for more.