Credit: NASA/JPL/Space Science InstituteFrom the website
"A crescent of Tethys displays two of the moon's large craters.
Penelope Crater can be seen at the top left. Antinous Crater is in the bottom left, in the far southern latitudes. Features on Tethys are named after characters and places from Homer's Greek epics."
For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov/ . The Cassini imaging team homepage is at http://ciclops.org/ .