islands

1) I haven't seen the map in Plan[e]t Engineering, but I've read the discussion in the archive and accepted that the Commonwealth was South America, and thought I had a fairly good grasp of the topography. But then I came across this sentence in Citadel, ch. V: "I did have the impression (though I could not be sure it was correct) that it [Ascia] was a single land mass, and not a chain of islands like our south..." Where does this fit in with what else we know about the Commonwealth's geography? Of course, maybe Severian just means that the south contains a chain of islands; but that's not what he says.