Hippalus Rimae
Hippalus (58 km) is the reminant crater in the lower RH corner. It is bisected by on of several broad rilles that track the circumference of Mare Humorum (sea of moisture, not 'humour'). Collectively these rilles are known as Hippalus Rimae. From right to left they are numbered I, II & III. Hippalus was a Greek navigator (c 120 AD). The prominent crater on the LHS is Campanus A (11 km)