The frill shark has a large mouth with 25 rows of 300 sharp teeth, six pairs of fringed gill slits, and a long, eel-like body that can grow up to 6 feet long. It's referred to as a "living fossil" because it's a member of one of the oldest living shark species.
Scully: On the old mariner maps, the cartographers would designate unexplored territories by simply writing "Here Be Monsters". Mulder: I've seen the same thing on maps of New York City. — The X-Files, "Quagmire"