I think the first is M. karwinskiana, or one of its subspecies, but probably just karwinskiana.
The second looks a bit worse for wear, but I'd suggest M. backebergiana. I can't quite see if it has 1 or 2 central spines, there is a second darker spine, but it might be radial rather than central. The darker epidermis suggests ssp. ernestii, but this is supposed to have only 1 central spine.