Coronavirus Updates: For the latest COVID-19 news and information, visit Penn State's Coronavirus Information website.
Image courtesy of Matthew Naedel.
Ridged upper-surface. Image courtesy of Matthew Naedel.
Ridged upper-surface. Image courtesy of Matthew Naedel.
Image courtesy of Jack Harper Slide Collection
Image courtesy of Jeffrey Borger
Image courtesy of Jeffrey Borger
Image courtesy of Jeffrey Borger
Image courtesy of Jeffrey Borger
Image courtesy of Jeffrey Borger