Several years ago, we found a really weird worm crossing the sidewalk. It was about 12 inches (30 cm) long, silvery-black in color, a bit slimy, and not lumpy or segmented like earthworms. It had a weird-looking head, somewhat arrow-shaped, with the arrow pointing forward. It had thin, black stripes going lengthwise down its body.

Well, after much hunting, we finally found out what this strange worm is:
It's a Land Planarian (Bipalium kewense), a type of flatworm, and it eats earthworms (yuck!).