As far as I understand it, a 9th planet was already guessed at in the late 19th century.
The Titius-Bode "law predicted a planet at ~ 38.8 AU in the 18th century. It's elliptical orbit would be off the chart on Russel's diagram, it's perihelion just cutting one of the corners.
dots are seen on the earth orbit too, in 210 the asteroid TK7 was discovered, moving 60 degrees ahead of the earth.
This is historic, The solar system is the only thing Russel got nearly right, more or less. Then he was not of the F&DS anyway. He missed his chance to produce a truly prophetic picture of the Solar system.