Zebra Mussel

Description:

As you can see from the pictures, there's a range of appearance as far as stripes and or coloring. The stable trait is the shape of the shell: D-shaped. They can be very sharp when split open, like these empty shells are, and the shell shape gives them strength enough to cut into your foot.

Habitat:

Freshwater reservoir.

Notes:

The third photo shows the two halves of shells open but still attached to each other. Most are just half of a shell.