Whoa . . . interesting photos! Thanks so much!!! My Mom has an older Rat Terrier that has a leision on his leg that looks like one of those---it never 'looked' like ringworm to me---but it's identical to that dark one on the leg, and he's always chewing at it and it seems to be spreading! I'm going to try an anti-fungal on it and see what gives . . . never thought of it before!
(Oh, he can't go to the vet---he chewed through a rabies pole wire once, and now they're all afraid of him).