Someone typed ritidiadelphus. What is missing?
heard as ritidiadelphus
spelled rhytidiadelphus
The h after the r, and the h in the ph near the end. The name is rhytidiadelphus.
What the ear did
Both h's are silent, so a listener has no way of knowing they are there. The first belongs to the Greek rho, which English writes rh in rhythm, rhino and rhubarb. The second belongs to phi, which English writes ph and says f.
R-H-Y-T-I-D-I-A-D-E-L-P-H-U-S
The full entry for rhytidiadelphus covers the name itself.