Thanks very much, Rowland, for the ID and information. Image moved from Polydesmida to new species page.

The low, rounded tubercles or pustules on the dorsal surface indicate that this millipede is Scytonotus granulatus (Say, 1821) (Polydesmida: Polydesmidae). The paranota (lateral segmental expansions on the dorsa) are a bit smaller on segs. 6-7, indicating that this is a female, and there are correspondingly 2 pairs of legs on that segment instead of one as in a male. S. granulatus occurs from Ontario & Wisconsin to South Carolina, northern Alabama, and the eastern fringe of Oklahoma. It even occurs north of Sault Ste. Marie, Ont.