The Nine Planets (both mirror sites I think) regarding the searches for Planets X.
http://seds.lpl.arizona.edu/nineplanets/nineplanets/hypo.html#planetx
Another short-lived trans-Neptunian suspect was reported on April 22 1930 by R.M. Stewart in Ottawa, Canada -- it was reported from plates taken in 1924. Crommelin computed an orbit (dist 39.82 a.u., asc node 280.49 deg, inclination 49.7 deg!). Tombaugh searched for the "Ottawa object" without finding it. Several other searches were made, but nothing was ever found.
http://www.solarviews.com/eng/hypothet.htm#planetx
During this period, other astronomers searched for additional planets. Another short-lived trans-Neptunian suspect was reported on April 22, 1930 by R.M. Stewart in Ottawa, Canada. It was reported from plates taken in 1924. Crommelin computed an orbit with a distance of 39.82 AU, an ascending node of 280.49°, and an inclination 49.7°. Tombaugh searched for the "Ottawa object" without finding it. Several other searches were made, but nothing was ever found.