The Anaerobic Belt is a band of worlds where oxygen is extremely low or nonexistent. Life persists in the form of anaerobic bacteria on most of these Earths. The Anaerobic Belt begins at approximately Earth West 130,000,000 and extends west.[1]
There are Earths in this belt populated by complex, acid-solvent based lifeforms, such as Earth West 161,753,428.[2]