From the "Frequently Asked Questions" -- if you go to copyright.gov, and search for "eco.gov" you can find this:
"Who can use eCO to register claims?
Anyone can use eCO to register basic claims to copyright, even those who intend to submit a hard copy(ies) of the work(s) being registered. Basic claims include literary works, visual arts works, performing arts works, sound recordings, motion pictures, single serial issues, groups of serial issues and groups of newspaper/newsletter issues. At this time, the following types of registration are not available in eCO: renewals, corrections, mask works, vessel hulls, groups of database updates, and groups of contributions to periodicals. For information about registering these types, see the Copyright Office website."