https://apnews.com/e70c4538d90ebee17c15ae547f61da10

MADISON, Wis. (AP) — Biologists discovered a cluster of rare mussels that could be more than 100 years old in the upper St. Croix River this past summer.

Wisconsin Public Radio reported Wednesday that biologists from the University of Minnesota, the Wisconsin Department of Natural Resources and the National Park Service discovered eight spectaclecase mussels in the river in August.