Further investigation has lead me to believe that the left most dark marking is likely Mare Sirenum and Mare Cimmerium, the larger dark area on the right side is likely Mare Erythraeum.? Between them, along the meridian is the region I mention above, Aonius Sinus and Phaethontis.? The image is north down (you can see the north polar cap) and mirror imaged (West to the left)....I think. Ha.
Many moons ago I used to have a small app on my PC that would show me a map of Mars surface features based on date and scope configuration...I don't recall its name though.? I wish I still had it.
