The main sea is Mare Crisium with Craters Peirce and Picard (right & left in upper half of Mare ). Crater Langrenus is at lower left corner of image.
Crater Peirce is 19km across and Picard is 23km across.
Information came from
http://www.inconstantmoon.com/cyclopedia.htm
Looks like a great site.
Cheers,
Duncan
